The tower where Sauron resides in Mordor in J.R.R. Tolkien’s The Lord of the Rings is Barad-dûr.
Barad-dûr is Sauron’s fortress in Mordor and the principal symbol of his power during the War of the Ring. Its name is commonly translated as “Dark Fortress.” The tower stands near Mount Doom, where the One Ring was forged and where it must ultimately be destroyed.
Sauron’s power is closely tied to the Ring, although Barad-dûr remains a major military and political center even when he is not physically present there. The fortress is guarded by Mordor’s armies and watched over by Sauron’s searching will.
Orthanc is the tower at Isengard occupied by Saruman, not Sauron. Minas Morgul is another important fortress in Mordor, while Dol Guldur is a separate stronghold in southern Mirkwood. These locations are distinct despite all being connected with the forces of darkness.