What is the name of Sauron's fortress in Mordor?

Sauron's fortress in Mordor is called Barad-dûr, a name commonly translated from Sindarin as “Dark Tower.” It is the chief stronghold of Sauron and one of the most recognizable landmarks in Tolkien's Middle-earth.

Barad-dûr stood near Mount Doom, or Orodruin, where Sauron forged the One Ring. Its foundations were strengthened by Sauron's power through the Ring, making the fortress extraordinarily difficult to destroy. In The Lord of the Rings, the tower represents Sauron's military authority and his control over Mordor.

The fortress was destroyed after Sauron's defeat at the end of the Second Age, although its foundations endured. Sauron rebuilt it during the Third Age after returning to Mordor. When the One Ring was finally destroyed, the power sustaining Barad-dûr failed and the fortress collapsed. A frequent mix-up is Minas Morgul, another fortress in Mordor, which was formerly the city of Minas Ithil and served as a stronghold of the Nazgûl.