Mountains' Graveyard

is a mountainous region that contains the bones of many giant creatures. It is a secret hideout of Madara Uchiha and later Tobi. During the Third Shinobi World War Obito Uchiha, after beeing crushed by a rock, somehow ended up in a tunnel connected to the mountain and before the start of the Fourth Shinobi World War, Kabuto Yakushi managed to locate the place while also using a trail of corpses to lead Anko Mitarashi's Search Team there as well.

Inside it is a laboratory, where Tobi keeps a massive storage of eyes, as well where he transplanted Itachi's Sharingan into Sasuke. Deeper inside the headquarters is where Madara cultivated the cells of Hashirama Senju into a clone to access his powers and where the Demonic Statue of the Outer Path rests ontop of it, though it can be summoned elsewhere if needed. The clone was first used by Madara as a life support system keeping him alive by feeding of the Statue's chakra and later to amplify the power of Tobi's army of White Zetsu clones.