The fortress ruled by Saruman in J.R.R. Tolkien’s The Lord of the Rings is Isengard.
Isengard stands in the southern part of the vale of the Wizard’s Vale, near the western end of Rohan. Its central stronghold is the tower of Orthanc, a remarkably hard black structure built by the Númenóreans. Saruman occupies the fortress and uses it as a base for military preparations.
During the War of the Ring, Saruman breeds large numbers of Orcs and Uruk-hai at Isengard. He also cuts down trees around the fortress to fuel his industry, damaging the landscape of the Ents. This destruction helps motivate the Ents’ attack under Treebeard.
The Ents flood Isengard and defeat Saruman’s forces. Afterward, the place is transformed into a green garden, while Orthanc remains standing. Isengard is therefore both a military location and an important symbol of the conflict between industrial exploitation and the natural world in Tolkien’s story.
The Sindarin name Angrenost means Iron Fortress, while Isengard is the common name used in the narrative.