Mountains' Graveyard

is a mountainous region located at the north-most region of the land between Takigakure and Otogakure. It has dense forestry and the bones of many giant creatures can be seen jutting out of it. It is the secret hideout of Madara Uchiha and later Obito Uchiha, who began acting under the alias "Tobi".

At 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 team there as well.

Overview
Some time after being defeated by Hashirama Senju, Madara set up a base here. As Madara was living off life support provided by the Demonic Statue of the Outer Path, White Zetsu clones were instead used to gather information from the surface world and carry out any other functions as they could travel through the earth. There were passages that seemingly led to different countries as Madara was able to have the White Zetsu retrieve a heavily wounded Obito who was in the Land of Grass. This passage was eventually closed off on Madara's orders and later smashed open by Obito by using the powers of the Demonic Statue of the Outer Path. Another part of the cave was destroyed by Sasuke Uchiha when he tested out his Eternal Mangekyō Sharingan.

When occupied by Madara, there was only Hashirama's living clone from which sprouted the Zetsu minions, the tree which grew from it and the Demonic Statue seated upon it, a large tree stump which Madara occupied, and a wooden bed on a single platform. On a wall also hung his gunbai, a kama, several giant shuriken, spare cloaks. Though Madara claimed there was no exits where they were, many hidden entrances and exits had been carved out, concealed beneath the bones of animals, or else etched into the walls.

Within the base there is also a laboratory where a massive storage of eyes is kept. Tobi brought Danzō Shimura's corpse here in hopes of retrieving Shisui Uchiha's Sharingan. He also transplanted Itachi Uchiha's Sharingan into Sasuke. Beneath the clone of Hashirama is a flooded cavern where the rest of the White Zetsu Army clones were stored.