Castle (城)

A castle (shiro) is a structure that was built as a strongpoint for defending against enemy attacks. It was not only a bastion, but also a storage location for foods, weapons and funds. A major castle was the residence of a commander and the center of politics and information. Castles were often built on mountains for pure defense, but sometimes also used to occupy strategically important places, such as roads and rivers. They are also known as citadels.

In Europe, China and other continents, there is a distinction between a wall surrounding a city and a battle site of soldiers, such as a fortress, and the former is called Stadtmauer in German and a city wall in English and the latter is called Burge in German and a castle in English. The character 城 means a walled city of the former meaning in China, but walled cities were not built in Japan, and were mainly used in the latter sense.

In general, the castle has the following features:

Defense mechanism
The castle is held if a sudden attack occurs or the military power is inferior.

Rule base
It was used as a symbol of domination or an outpost for expanding territories in enemy territory.

Residence of the monarch
A castle was the residence of a monarch and also the base for residents.


There were various castles, such as ancient moat settlements and modern castle towers with stone walls. The forts and gun batteries at the end of the Edo period may also be included in castles. A camp with Kuruwa (walls of a castle) may be called a "castle." Construction consisted of building (civil engineering) of moats and earthen walls and construction of gates and walls. Houses, turrets (citadels) and keeps were also included in the construction.

Samurai were professional warriors in medieval Japan. A daimyo (feudal lord) and his family lived in a castle and together with women who took daily care of them. A large citadel often included a surrounding town. Edo-jo Castle is the largest castle in Japan. It is said that there were a lot of castles in various parts of Japan and there were several hundred thousand castles including small forts until Ikkoku Ichijo Rei (Law of One Castle per Province) was issued in 1615. Mansions and residences such as mansions built on flat ground during the medieval period and modern times do not include castles, but residences or mansions with towers which were built similarly to castles are regarded as castles.

Origin of word "shiro"

The character "城" is currently pronounced "shiro" by kun-yomi (Japanese reading of character), but it seems that historically there was no native Japanese word "shiro." From ancient times to the early medieval period, the character "柵" was also used in addition to "城" and pronounced "ki" (城柵) (-> 城(ki)). For example, Ono-jo Castle (Chikuzen Province) near Dazai-fu (local government office in Kyushu region) was called "oononoki" and Dewanoki (Dewa Castle) in Yamagata Prefecture was called "dewanoki." The character 城 was pronounced "jiyau (jou in modern kana usage (as laid out by the Japanese government in 1946))" and the character 柵 was pronounced "saku" later.

The origin of word "shiro" seems to be as above. Since Yamashiro Province (southern part of Kyoto Prefecture) was located behind Nara-yama (Mt. Nara) as viewed from the capital of Nara, it was named "yamashiro" which meant 'behind a mountain' and was spelled "山代" in ancient times and "山背" in the seventh century. When Emperor Kanmu transferred the capital to Heian-Kyo, he wrote "此国山河襟帯、自然作城" (this country was surrounded by mountains and rivers from which nature formed a castle), recognizing that this country was a castle of nature. An imperial decree as follows was carried out on December 15, 794.
A new era name should be established due to the picturesque scenery.'
山背国 should be renamed to 山城国.'
Since 'A new era name should be established,' it seemed that the characters were changed and the pronunciation was changed to "yamaki," but in fact, only the characters were changed to "山城" and "yamashiro," "城" was pronounced "shiro" only for the word "山城." A place where a castle was built on a mountain was called "yamashiro," and when the era when a castle was built on a mountain to defend territories came, "城" was pronounced "shiro" during the latter medieval period. "城" was pronounced "shiro" in "Bunmeibon setsuyo-shu" (a plain dictionary in Bunmei era) in 1474.

Up to ancient times

In the Yayoi period in Japan, many moat settlements or citadel villages or upland settlements were built in high places, such as mountains, but declined with advances of political unity.

The first appearance of the word castle in literature is Mizuki (water fortress) built by Emperor Tenchi in 664, and plenty of castles, including ones not found in literature, were built in the area from the northern part of Kyushu to the coasts of the Seto Inland Sea in this age. In the Tohoku region, where the war against Emishi (natives in Ezo) continued, castles that doubled as a military base and an administrative office, such as Taga-jo Castle, Dewanoki (Dewa Castle), and Akita-jo Castle, were built in the seventh to ninth centuries.

These castles came from the Chinese concept of walled cities and were used as provincial capitals, but walls were replaced by fences because of poor castle wall construction technology. These castles began to crumble as the ritsuryo system collapsed, and the castles were built in the age of samurai as military bases.

Medieval period

In medieval Japan, castles developed for two purposes: in order to defend the samurai residence during peace time and defend from attack by armies from around steep mountains during war time.

There were many of the latter mountain castle types until the early Sengoku Period (Period of Warring States) (Japan). A feudal lord who usually resided in a castle was confined in a strong mountain castle as a defensive base when he was attacked by enemies. The mountain castle was called Tsume-no-shiro (alias of Honmaru) compared to Negoya (small-scale castle town) at the foot of a mountain.

The residence where the former lord lived in peacetime was built at the foot of a mountain. Castles were called 'Negoya' (small-scale castle town), 'mansion (yakata/tachi/tate),' or 'house' in some regions, and were surrounded with walls and had turrets at the gate, practically functioning as castles. The houses of vassals, farmers and townspeople (a primitive castle town) were built around such castles.

The number of castles increased greatly from the middle of the Sengoku period, hirayamajiro (castles built on a hill or low mountain surrounded by a plain) or hirajiro (a castle built on flatland) became dominant, and mountain castles decreased because they were useful for defense, but not appropriate as a base for political power.

This period is characterized by the fact that facilities called 'mura-no-shiro' (village castles) were built in various parts of Japan. Local residents built them as escape facilities during war time because wars broke out frequently, and they functioned as military facilities used to carry out resistance movements or struggled with adjacent villages. For these facilities a flat space was created on top of a mountain and were simple and small compared with pure military castle facilities.

Modern times

The form of stone walls, castle towers and turrets (citadels) which were main elements of castles at the time, were created when Hisahide MATSUNAGA built Tamonyama-jo Castle and Shigisan-jo Castle after the end of Muromachi period or when Nobunaga ODA built Azuchi-jo Castle. Hideyoshi TOYOTOMI built Osaka-jo Castle and Fushimi-jo Castle later, and the general image of 'castle' with castle towers, stone walls, squares and umadashi was completed and castle culture in Japan prospered. This form of castle was historically called shokuho period fortress. The shokuho period fortresses were not built throughout the country, but were mainly built by daimyo under control of Nobunaga ODA and Hideyoshi TOYOTOMI as the name suggested. The daimyo in the Sengoku period in Tohoku, Kanto, Shikoku and Kyushu built their castles according to the circumstances of each region. The Toyotomi and Tokugawa governments let daimyo in various parts of Japan build castles positively as Tenkabushin (construction order by the Tokugawa shogunate). The method of construction of shokuho period fortresses came into wider use and they developed into eclectic type fortresses by adopting parts of the shokuho period fortresses. There were many examples in which local fudai daimyo built pure shokuho period fortresses.

Since Ikkoku Ichijo Rei (Law of One Castle per Province) was issued in the Edo period, each daimyo retained only one castle and destroyed others. Most of the castles that were destroyed were medieval mountain castles. Each daimyo destroyed the castles of his vassals actively and made them live in the castle town to establish modern control and order. The castle functioned as a political center, a symbol of authority and power of lords, or a local land mark rather than a military base. In addition, the modern castle towns were built as vassals, merchants and craftsmen inhabited castle towns due to their being a center of economy. Most of the current castle towns were built in the Keicho era in keeping with this trend. Most modern citadels were also constructed in the Keicho era. However, castles and castle towers were often burnt out, but they were rarely reconstructed because most domains ran into fiscal difficulties or were restricted by the bakufu according to Buke Shohatto (code for the warrior households).

The facilities called jinya (regional government office) in the Edo period and forts and gun batteries built in various parts of Japan as a countermeasure against foreign ships were also kinds of castles. There are several castles which were built under the influence of the western castle construction style for artillery battles and the bastion-type fortresses (such as Goryokaku), but except for Goryokaku, they were not fit for actual fighting because of reduced construction period and budget, and the construction work for most of them was suspended by Haihan-chiken (abolition of feudal domains and establishment of prefectures).

Modern times

In the Meiji period, the citadels in each region were destroyed according to haijorei (an order to abandon castles) in 1873 or burnt due to being abandoned by management or collapsed after materials were seized by the Imperial Japanese Army. Government offices were often established or new parks or shrines were built at castle sites, and the Imperial Japanese Army was stationed at almost all the castle sites in the main cities. The castle sites used as garrisons were targeted by the United States Armed Forces during the Pacific War (The Greater East Asia War) and citadel constructions, such as castle towers, turrets and gates of Nagoya-jo Castle, Wakayama-jo Castle and Hiroshima-jo Castle, which were built before the Edo period, were burnt out in air raids or with atomic bombs. The towers of twelve castles (twelve castle towers remain now), such as Himeji-jo Castle and Kochi-jo Castle, and towers, gates and others of Osaka-jo Castle and Nagoya-jo Castle are still in existence. Many gates and turrets of citadels escaped from being damaged in fires and wars and still exist to this day, in contrast to castle towers, with most of them being designated as national important cultural property.

Reconstruction and restoration

Citadels were restored, especially castle towers that were built from before the war in the Showa period, reconstructed imitation keeps were built in Sumoto-jo Castle and Ueno-jo Castle and a reconstructed tenshu (keep) that was built on Osaka-jo Castle. Castle towers were mainly reconstructed after the war in the Showa period, in the 30's and 40's of the Showa period during the 'castle tower reconstruction boom' or 'castle reconstruction boom' after the construction of the reconstructed tenshu (keep) of the Toyama-jo Castle in 1954, but reconstructions at historical sites were often requested to be faithful to the original according to the policies of the Agency for Cultural Affairs from 1988 and when the Takeshita cabinet carried out the Furusato creation project, restorations and reconstructions in wood based on historical materials were performed in principle after the reconstruction of Sanju Yagura (three tiered turret) of Shirakawa Komine-jo Castle in wood in 1990.
The tower of Kakegawa-jo Castle, a group of citadel structures of Kumamoto-jo Castle and Sasayama-jo Castle dai-shoin (large study) were reconstructed based on historical materials, and this period was called the 'restoration boom in the Heisei period' or "the second restoration boom.'
There were cases in which castle towers, turrets, gates, palaces, earthen walls and stone walls were reconstructed or excavated citadels of the medieval and Sengoku periods were reproduced during this period. However, since the restoration work by traditional techniques infringed on the Building Standards or Fire Prevention Act, there were problems in that entry into gates and turrets was restricted or castle towers could not be constructed due regulations on building height for disaster prevention, with modern techniques being partly introduced or reconstruction plans given up as in the case of Sanju Yagura (three tiered turret) of Sendai-jo Castle.

The interior of the restored buildings is mostly open to the public as a folk museum or a historical reference library.

(For details on restored castle towers, reconstructed castle towers, reconstructed imitation keeps, and donjon-like buildings, refer to the construction of modern and present donjons.)


A scholar of military science in the Edo period classified castles based on topography into three types: 'Hirajiro' (a castle built on flatland), 'hirayamajiro' (castles built on a hill or low mountain surrounded by a plain) and 'mountain castles.'
This distinctions are not clear.


Basic design for castle construction is called nawabari (castle plan; general term for the layout of a castle and its component structures) or keishi and the most important element is arrangement of Kuruwa (walls of a castle). The word "nawabari" is derived from verification of the layout of Kuruwa by roping off in the field. Some scholars of military science made various classifications and analyses in modern times. The basic forms of nawabari (castle layouts) include the following: Rinkaku (contour) style, where the Kuruwa is positioned concentrically along the Honmaru (castle keep), the Ninomaru (second bailey) and the Sannomaru (outer part of the castle); Teikaku style, where the Honmaru is positioned closer to a mountain, sea or river (ushiro-kengo), the central compound is positioned adjacent to the castle walls, and additional compounds are positioned around the Honmaru; and Renkaku style, where independent Kuruwa are placed in a row along the ridges. In fact, they often take the form of the compound.



An area surrounded with a moat, an earthen wall or a stone wall was called kuruwa, and a castle had several kuruwa. It was also called maru in the Edo period. The kuruwa that plays the most important part in defense is the honmaru (hon-kuruwa/main enclosure), and in addition to it, mostly ninomaru (second bailey) and sannomaru were built. Some castles had yagura kuruwa, mizute-kuruwa (a small lot in a castle, including a well or reservoir), tenshu-kuruwa, nishi no maru (a castle compound to the west of the main compound) (retreat for daimyo's old age) and so on. An expanded umadashi was called umadashi kuruwa and an independent kuruma adjacent to a castle was called dekuruwa (kuruwa, a small lot, provided at a position projecting from a group of main kuruwa) or demaru (small castle or tower built onto and projecting from a larger castle). They include the sanada-maru (sanada barbican) in the Siege of Osaka and nishi-demaru (defense strongpoint) of Kumamoto-jo Castle.

In general, each kuruwa of a mountain castle was so small that only limited facilities could be installed, but each kuruwa was large in a hira-jiro (castle built on the level ground) so that large facilities, such as a palace, could be built there.

Sotoguruwa (outer compound)

When the castle changed from a medieval period temporary military base to a permanent base of rulership, a defense line was often established outside the functional component (uchiguruwa (the central portion of a castle compound)) of the conventional castle to defend the castle town and vassals. This was called 'gaikaku' (outer compound), 'sotoguruwa' (outer compound) or 'sogamae' (defense facilities such as moats and mounds). Generally, a castle refers to only the uchiguruwa and since sotoguruwa includes natural topography (mountains and rivers), its range was often uncertain.

Kirigishi (bluffs), moats, earthen walls and stone walls

Kirigishi (bluffs) were used as basic defense facilities composing an initial mountain castle, but moats and earthen walls were used frequently and stone walls came into wider use. There are several kinds of moats: water moat, karabori (dry moat), unejo tatebori (a series of parallel trenches running up the sides of the excavated mountain), and the earthen wall, which was also called doi, was an outer wall made of earth dug out from a moat. A fence or wall may be constructed on top of the earthen wall and sakamogi (fence made of thorny or steepled branches) was placed on a slope to prevent enemies from entering and reinforced defenses. Stone walls were used at several important parts of a citadel even in the medieval period, but stone walls reinforced by stacking stones on the surface of earthen walls developed as the need arose to build heavy turrets near the citadel in the Azuchi-momoyama period. After Azuchi-jo Castle had been built, many large stone wall structures were built in western Japan as civil engineering technology developed.

Koguchi (a castle entrance)

An entrance to a castle is called koguchi. The entrance path is mostly winding and earthen walls called shitomi (timber shutters or doors that generally have vertical and horizontal lattice attached to the exterior surface and sometimes to the interior surface as well) or kazashi were built in front of the castle gate or with koguchi to prevent people from being able to enter straight into the castle. An ote-mon gate (main gate) was built at the koguchi in front of the castle (usually at the south of a modern citadel) and a karamete-mon gate was built at the rear koguchi. Since a koguchi was an entrance for johei (castle garrison), but also for enemies, it was especially protected. An entrance with a vallate square space and double gates was called a masugata koguchi (square entrance). A small kuruwa surrounded by a moat was built as a bridgehead on the opposite side of the moat outside the komuchi and was called umadashi (a type of defensive gateway barrier of castles).

An earth-paved bridge or wooden bridge was built over the moat at the koguchi that faced enemies, the plates of the wooden bridge were removed or broken to separate the inside from the outside of the castle or the inside from the outside the citadel, or a special bridge designed to be mobile was moved. Mobile bridges include hikuhashi (wheeled bridge that could be retracted to prevent enemies from entering), such as sorobanbashi (alias of 引橋 (hikuhashi)) and kurumabashi (a type of 引橋 (hikuhashi)), hikihashi leading to the inside of the citadel, and drawbridge (a bridge that could be pulled up with gateposts of koguchi).

Fences were built to partition kuruwa or on top of stone or earthen walls for defense. Mud walls, wooden fences, nurikomi-bei and so on were used in the medieval period and plastered walls and namako-kabe (a wall with flat tiles nailed down on the wall surface and jointed with plaster) were used to prevent a fire in modern times. Fences and turrets had small windows or loopholes called 'sama' or 'hazama' to fire a gun or launch an arrow. There were circular loopholes, rhombic loopholes, loopholes shaped like a shogi piece, shinogi hazama (triangular loophole), hako hazama (box-shaped loophole), and so on according to the shape of windows, as well as ishisama (stone loophole used to fire a gun through the castle wall) that was cut in the top of a stone wall under a fence. They were divided into oillet, teppo sama (loophole to fire a gun), taiho sama (loophole to fire a cannon) and so on according to their use.

A turret is a structure that functions as an observation (lookout) platform, warehouse and defense. Turrets were usually named by giving them numbers or directions, such as tatsumi-yagura, ushitora-yagura, and inui-yagura turret, and some turrets were called tsukimi-yagura turret (used for monitoring a castle entrance), tsukimi-yagura turret, taiko yagura (drum turret) and so on according to their use. Two-story turrets were normally used in modern citadels and small three-story turrets were used for large castles for the sumi yagura (corner towers) that were built at corners of a citadel, but were cases in which a turret that had a structure equivalent to tenshu (castle tower) were built, for example, the three-story turret in the honmaru (the keep of a castle) of Osaka-jo Castle and the five-story turret in Kumamoto-jo Castle.

Tenshu (the keep of a castle)

The tenshu that was positioned as the final strongpoint of a citadel and a symbol of a castle was said to be evolved from a large watchtower turret.

There is a theory that states that it was named after enshrinement of Tamonten, Bonten, or Taishakuten (gods) of Buddhism or that the house of a castellan was called 'densu' (taking care of the tasks in the Buddha hall and the main hall). There is a theory that states that the first appearance of the word tenshu in literature is Settsu-Itami-jo Castle or Yamato Tamonyama-jo Castle of Hisahide MATSUNAGA or the tenshu of Azuchi-jo Castle of Nobunaga ODA, but its origin is not clear. Tenshu with various forms and shapes were built, but the peak of castle construction was the Battle of Sekigahara, and castles 20 to 30 meters high, like Himeji-jo Castle, were built in western Japan the in those days.

Okinawa Prefecture and Amami Islands

There were gusuku (Okinawan castles or fortresses) in the former Ryukyu Kingdom area of Okinawa Prefecture and Amami Islands. There are various theories that state that they were originally sanctuaries or settlements. Most gusuku contained sanctuaries called mitake (Okinawa). Chinenmori-gusuku Castle is said to be a castle in which a god appeared for the first time in Okinawan poetry anthology "Omoshirososhi" (Interesting Literature). Shuri-jo Castle whose buildings or relics are being restored are the largest existing remains among citadels in the Ryukyu islands, and was selected as a world cultural heritage together with Naka-gusuku Castle and Nakijin-gusuku Castle.


Chasi (the Ainu word meaning fort, fence, barrier, etc.) in Hokkaido correspond to castles. The chasi built by the Ainu tribe exist in various parts of Hokkaido. They were basically used as fortresses to fight with other Ainu groups, wajin (Japanese: persons whose origin is the Japanese mainland) or Uilta. They were also used for ceremonies and had various functions.

Castles in Europe

Fortress construction technology changed greatly with the advance of explosives, cannons and guns in the fifteenth to sixteenth centuries. Since the dawn of history, basic elements of defense facilities, forts, castles and fortresses were walls and towers. Enemies were prevented from entering the walls and the enemies were attacked from towers by taking advantage of their height, which increased the power of arrows, while simple stones and logs could be used as weapons when gravity was used. The attackers would attempt to destroy the walls, but it took much labor and time and the defenders had precedence.

However, when cannons and guns came into use, the power of bullets with gunpowder reduced the superiority of height and the relatively thin walls were destroyed easily with cannons. The functions of the fortress were separated from the functions of the castle, thickness took precedence over height for the fortress, and star-shaped ryoho shiki (a style based on the fortification of Vauban in France) fortresses became dominant as permanent fortresses and trenches became dominant as field fortresses. On the other hand, the castles that emphasized interior comfort, grandeur and luxury rather than defense functions, were elegant and had many windows built into them.

Ancient time
When civilization developed and cities were built in the area including the Near and Middle East, a castle wall was built around a city to defend the city and establish a military base. Such sights could be seen in many places, not only in lands around the periphery of the Mediterranean Sea (which was the center of culture at the time), but also in other places; for example, the "Gallic War" by Gaius Julius Caesar described many scenes in which Gallic cities built on sites with a steep slope were attacked. Areas where the Roman forces built up temporary strong points with sufficient defense capabilities to support their marches could be regarded to be a kind of castle.

The materials of castle walls vary according to regions, times and degrees of construction techniques, for example, sun-dried bricks, burnt bricks, stones, wood and earth. The Gallic castle walls described in the "Gallic War" mainly comprised of wood, and stone buildings were fully introduced into Northwest Europe after being Romanized.

Medieval period

When the Frankish kingdom split and loosened its grip and the invasion by Normans and Magyars intensified, local lords became independent and reinforced the defense of their territories and residences. At first a fence was built or a moat was dug around a residence, and structures called castles were built starting at the end of the tenth century.

Most castles were simple and composed of wood, and Motte and Bailey type were typical (refer to Figure a.). A moat (mostly empty) was built by digging a plain or hill and a mound or knoll was built with the removed earth. The mound was solidified with clay and a wooden or stone tower (keep) was built on top of it, and the knoll was surrounded with a wooden outside wall to create castle facilities, such as warehouses and houses. This castle could be constructed very easily and there was a case in which it was built in eight days with a sufficient number of people. These castles were used in the western part of France and also built all over England after the Normal Conquest.

Most cities became fortified cities within castle walls.
(Old cities used the reconstructed castle walls of the Roman period.)
(Refer to Figure b. Carcassonne.)

Castles with keeps and outside walls composed of stone were built in the eleventh century, but since the construction of stone castles was time-consuming (several years) and expensive, they were mainly built by kings or nobles, and wooden castles remained in local regions. A square tower was installed on a stone wall to protect it.
(Refer to Figure c. Tower of London and Figure d. Oxford Castle.)

In the age of Christian Crusade in the twelfth century, the Byzantine and Arabian techniques in the Middle East were introduced and castle construction technology changed drastically. Concentric castles were designed so that an inner wall was built inside an outer wall, two or more walls were built concentrically around the keep, and inner walls became higher so that the inner defense was effective even if the outer wall was destroyed. The walls became thicker and towers became cylindrical to resist impacts. Typical castles are Krak des Chevaliers Castle (Castle of the Knights) and Château Gaillard.
(Refer to Figure e. Krak des Chevaliers Castle.)

Concentric castles evolved into Edward type castles in the thirteenth century, which Edward I (King of England) built to govern Wales. A gate house came to have the functions of the conventional keep.
(Refer to Figure f. Harlech Castle.)

Modern times

However, when cannons and guns came into wider use in the fifteenth century, the power of bullets with gunpowder reduced the superiority of height, while cannons destroyed high and relatively thin walls with ease while high buildings became excellent targets for cannons. The thickness of castle walls was considered more important than their height, and the height of inner structures was made low, and there was no space for government offices and houses. As a result, a fortress that functioned as a military base was separated from those that functioned as a castle, such as houses of nobles and government offices, and low star-shaped ryoho shiki (a style based on the fortification of Vauban in France) fortresses were built.
(Refer to Figure g. Oradea.)
On the other hand, the castles that emphasized interior comfort, grandeur and luxury rather than defense functions, were elegant, and many windows were installed. The image of the present European castle originated from those built in modern times.
(Refer to Figure h. Chateau d'Usse and Figure i. Schloss Neuschwanstein.)


A castle in China originally meant a castle wall and referred to the defense facilities surrounding residences, such as cities and villages. In Chinese, cities are called 城市 (fortified towns) and the castles found in Europe and Japan were called 城堡 (castles and forts). The castle wall is called josho (city wall).

A large castle was divided into an inner castle that surrounded a palace where the governor lived and an outer castle that surrounded the entire city, and the inner castle was called a castle and the outer castle was called an enclosure, and the whole structure was called a citadel. The Great Wall of China was built on the frontier to protect against invasions by northern equestrian tribes. Barriers that are located at strategic points of traffic are important as fortresses with long, large and strong walls, though they are not called castles.


Castle walls were originally mud walls made using wood frames and the wall of Chang'ancheng of T'ang-Dynasty was a long and large dosho (mud wall) with a total length of 27 km. The strength of castle walls came to be more important later in the period, and most castle walls after the Ming dynasty which remain as ruins in various parts of China were made of solid bricks. There was a passway where soldiers could move on the top of the wall and a mud wall called josho was built with slits to shoot enemies climbing on the wall. There were projections called 'bamen' (overhang of a castle wall) at regular intervals, which were used as forts for attacking enemies from the side.

Gates were installed on the castle wall to enter and leave the city. The stone foundation was excavated to form a tunnel ('Ketsu' (gate provided with Rokaku (multi-storied building) in ancient China)), on which a wooden multi-storied building was constructed with a 'tablet' showing the name of the gate. Most gates have a double structure and a small semispherical enclosure in front of the gate to drive away the enemy. This is called 'ojo' (fortress or a checkpoint in ancient China) which is found universally in all parts of the world, and corresponds to 'koguchi' in citadels in Japan. Since the enemy must enter the ojo to attack the city, soldiers could shoot them from walls and jiànlóu (watchtower built on ojo).

When the People's Republic of China was founded, walls were demolished in most cities to make way for the expansion of city areas or as a result of criticism for blocking modernization, but the walls are preserved in some cities, such as Xian City and Pingyao.

Korean peninsula

The castles in the Korean peninsula are classified into two types: mountain castle in a form specific to Korea and upuson with city walls, which are greatly influenced by China, but dominated later in the period. There are few perfect upuson because of the mountainous terrains, and many of them are small fortresses with an eclectic style. Enan-jo Castle that withstood the siege of the Japanese military during the Bunroku-Keicho War, and Jinju Castle that also held against Japan's attack are an example of those castles with an eclectic style. It is said that Suwon Castle in the Suwon city of South Korea for now aimed at the originality of Yi Dynasty Korea.

There were many castles built by Japanese forces in the southern region during the Bunroku-Keicho War, but they are known as wagon (Japanese-style castles), due to the considerable economic development in recent years in South Korea, many of these wagon have been destroyed despite being important historical sites, due to the strong anti-Japanese sentiment.

Middle East

Hussar Romero - citadel of the Ottoman Empire.

Day of the castle

On April 6 The Japan Castle Foundation established the "Day of the castle" project in the fiscal year 1974. It conducted a nationwide campaign in 1992, and now has much to do, such as holding free admission to events around the towers in the castle. Cherry blossoms bloom in many castles on this day.

Himeji City established April 6 'Shiro no hi' (Day of Castle). With a focus on events in Himeji-jo Castle (an event in Himeji Castle) the inside of the turret was opened to the public since 1990.