Mountains' Graveyard

Madara Uchiha possess a headquarters that also serves as a stronghold for his organization, Akatsuki. Inside is laboratory, where he keeps a massive storage of eyes, as well as performed a transfer of Sharingan from Itachi Uchiha to Sasuke Uchiha. Outside of the main gate of the headquarters is a large bone structure, where Sasuke sat on once to think about his past with Itachi. The outside is surrounded by walls of the headquarters building itself.

Kabuto Yakushi approached this place to offer (or rather blackmail) Madara into an alliance, but he left a trail of corpses to allow Anko Mitarashi and her team to the headquarters.