Reii

Reii (霊井, Spirit Well) is a secret subterranean training ground and base of operations located on a mountainside on the Unohana Clan's forest. It’s existence is only known by four persons, Raiden Unohana, Nanashi, Mayuri Kurotsuchi Kisuke Urahara. A number of barriers and seals surround this area to keep it in hidden.