The cave is shaped like a drum, around 96 m deep and the entrance is somewhat hidden in the Aokigahara forest. Its inner walls are permanently frozen, the temperatures inside are only between −2 ° C and +3 ° C all year round, and around +11 ° C in the entrance area. The Dragon Palace Cave is home to rare species of spiders that are adapted to permafrost .
In the large single chamber is a sanctuary in the form of a Shinto - shrine , the Senoumi -Schrein ( セノ海神社 Senoumi yashiro ). It is dedicated to the goddess Toyotama-hime no Mikoto , who is one of the daughters of Kami Watatsumi . The sanctuary has been a local place of pilgrimage for a long time , pilgrimages are held there every August 2nd . There is a legend about the cave that a dragon god ( Ryūjin , partly equated with Watatsumi) lived in it and that in times of drought the local farmers asked him for rain. The cave itself has been a protected natural monument since 1929 , and entry is usually prohibited to the public because of its religious significance and the risk of collapse.
- Hajime S. Tori: A Consideration of the Distribution of Some Troglobionts in Japanese Caves . In: Japanese Journal of Zoology: Nihon Dōbutsugaku Shūhō, Volumes 12-13 . Science Council of Japan, Tokyo 1956, ISSN 0368-2889, p. 559.