The Ancient City (Kyuuto or Kyuu Miyako, 旧都) is a large village in Hell, first seen in Subterranean Animism. It is situated between the bridge to Hell, guarded by Parsee, and the Palace of the Earth Spirits, where Satori and Koishi live. The buildings appear to be modeled after traditional Japanese houses, and the streets appear to be lit with fiery hanging lanterns. Although the city is built underground, it is still able to receive snowfall.
The Ancient City is populated primarily by oni, who moved underground long ago in order to avoid humans. Many oni, such as Yuugi Hoshiguma, can easily be found partying in the streets here. Suika Ibuki most likely lived here before moving to Gensokyo. Aside from the oni, many other subterranean youkai can probably be found here on occassions, as Yamame Kurodani mentions that the city doesn't turn away visitors.