Nippara Cave

Nippara Shōnyūdō (lit. 'Nippara limestone cave'), located in Nippara, Okutama, Nishitama District, Tokyo, Japan, is a limestone cave. It is over 1270m long from the entrance to the end, and it measures 134m from the depths to the ceiling. It has been registered a natural monument in Tokyo; equally large as Roukokudō, the two caves are known as one of the largest caves in the Kanto region. The cave flourished as a sacred mountain in the past and is a well-known tourist site as of modern times. The cave is opened throughout almost the entire year excluding between 30 December and 3 January.

Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).