Mountains' Graveyard

is a mountainous region, that contains the bones of many giant creatures. It is a secret hideout of Madara Uchiha. Inside it, is a laboratory, where Madara keeps a massive storage of eyes, as well where he transplanted Itachi's Sharingan into Sasuke. Also, the Demonic Statue of the Outer Path rests inside a room, though it can be summoned to elsewhere if needed, as Nagato did so in the Land of Rivers hideout. Deeper inside the headquarters is where Madara cultivated the cells of Hashirama Senju to access his powers, as well as to create an army of Zetsu.