Tsubaiotsukayama-kofun Tumulus (椿井大塚山古墳)

Tsubaiotsukayama-kofun is a tumulus located in Yamashiro Town of Kizugawa City, Kyoto Prefecture. It was built at the end of the third century and is the largest keyhole-shaped tumulus in the Yamashiro region.


It has been destroyed to such extent that its precise original size is yet unknown. The JR Nara Line runs through its round part.

Shape and Size
This tomb mound is estimated as follows: It was approximately 175 m long; the round part was approximately 110 m in diameter, 20 m in height; the rectangular part was approximately 80 m long, and approximately 10 m in height. Its rectangular part is open like a pot, and no moat has been found. A tumulus without a moat of water is very rare in the Kinai Region (countries near Kyoto). It was built in a hill, and clay was partly piled up to make the mound. Most of the mound makes use of the natural rise of the land, or a 'hill,' so it is completely part of the hill. This kind of structure is said to be found in many of the oldest tumuli.

Its burial chamber is a stereotyped pit-type stone room and houses a large half-cylindrical trough type wooden coffin.

Time of its Building

It is a keyhole-shaped tumulus built during the beginning of the Kofun period. Yukio KOBAYASHI categorized the Sankakubuchi Shinjukyo Mirror (Mirror with Triangular Rim, Gods and Animals) into seven types, and he determined this tumulus was built at the end of the third century, because the excavated goods included mirrors of those types from the oldest to the fourth latest categories. Today, formulated keyhole-shaped tumuli are considered to have been first built in the beginning of the second half of the third century, a little earlier than this the Tsubaiotsukayama-kofun Tumulus was built.

Funerary Goods

In 1953, when construction of expanding the railroad width of Kokutetsu (Japanese Railway) Nara Line was under way, this pit-type stone room was accidentally discovered, and it revealed 32 Sankakubuchi Shinjukyo Mirrors, the largest number at that time. Armor and a total of 36 or more mirrors including two Naiko Kamonkyo Mirrors (Mirrors with Linked Bow Pattern), a Hokakukikukyo Mirror (Mirror with TLV Pattern), and a Gamontai Shinjukyo Mirror (Mirror with Figures of Deities and Sacred Animals) were excavated. The number 36 or more was estimated from the fact that a few fractions of other mirrors were found and from the possibility that some items were lost because of grave robbing. The practice of placing many bronze mirrors in a coffin rapidly spread in the western and Chubu region of Japan during the beginning of the Kofun period. Those mirrors are considered to have been manufactured in a particular place or region over a short period of time.

The oldest Tosu (a small knife) in Japan was also found.

Excavated articles from this tumulus include: (1) weapons and armor: seven or more iron daggers, more than 10 iron swords, seven or more pikes, about 200 iron arrowheads, 17 bronze arrowheads, and a suit of iron armor; (2) tools and farming utensils: three iron sickles, 10 iron adz, 17 iron knives, seven or more iron yariganna (spear planes), eight or more iron cores, and three or more iron chisels; (3) fishing gear: more than 10 iron harpoons, a few iron fish spears, and an iron fish hook. An iron article that is suspected to be an iron-made crown was also found.

The Deceased

This tumulus lies to the right side of the Kizu-gawa River, one of the tributary rivers of the Yodo-gawa River. It held all the fishing gear that had been used since the Jomon period (about ten thousand years before third century B.C.): Harpoons, fish spears, and fish hooks. There is a place called Funado (literally, ship door) to the southwest. From these facts, the owner of this tumulus is thought to have controlled ships and ports in this region.