Shumidan is an altar to place a principal image in Buddhist temples, which is one step higher than other places and is used to place Buddha statues and other figures. It originates from Mt. Sumeru (in Buddhism - said to be the highest mountain rising in the center of the world).
The upper space of Shumidan is regarded as an area of Buddha, and Buddha statues are placed either directly on an altar or in a zushi or kuden (both are cupboard-like cases with double doors in which an image of (the) Buddha, a sutra, or some other revered object is kept at a temple) on a Shumidan. There are Wa-yo (Japanese style), Zenshu-yo (Zen sect style) and Setchu-yo (mixed style between Japanese style and the features of the Zen sect style). There are two types of Shumidan; the higher one is made such that the statue is placed directly on the floor while the lower one is made such that the statue is placed on the altar. Most of the temples adopt the former style and the latter style is merely seen except for temples of the Nichiren Sho Sect.
The word 'Buddhist alter' originally referred to Shumidan, but in medieval times the Buddhist alter in Buddhist temples came to be called 'Shumidan' and the zushi where Buddha was enshrined in houses came to be called the 'Buddhist alter.'
The platform to place and enshrine Buddha in Buddhist altar is still called 'Shumidan' at present.
The Chuson-ji Temple Konjiki-do (golden hall)
In the Chuson-ji Temple Konjiki-do (golden hall) in Iwate Prefecture, there are three Shumidan (Buddhist altars). An academic investigation in 1950 showed that the coffins of FUJIWARA no Kiyohira, Motohira and Hidehira and a bucket for the severed heads of Yasuhira, the fourth head of the Oshu-Fujiwara clan, were placed under Shumidan. It is one of the most famous Shumidan in Japan.
The Cineration into Shumidan
The cineration under the floor of the Shumidan (an altar to place goshin-ei (portrait of Shinran)) of Shinshu-honbyo Mausoleum (the Higashi Hongan-ji Temple) is called 'the cineration in Shinshu-honbyo.'
A person who makes a particular contribution to the head temple is given 'the certificate for cineration to Shumidan' in token of its gratitude. At present, it is given to believers who donates more than 120,000 yen.