One of the most important structures in Osgiliath, the ancient capital of Gondor. It was also known as the Dome of Stars, and within its hall stood the Master Stone, greatest of the four palantíri of the South-kingdom. In the early years of Gondor, the Dome appears to have held the Great Hall of Osgiliath, the throne room originally used jointly by Isildur and Anárion.

The Dome was seriously damaged in the civil wars of the Kin-strife, and in III 1437 the Tower of the Dome was destroyed and its palantír lost. The Dome itself is not mentioned after this burning of the city by Castamir, and by the time of the War of the Ring, probably no more than ruins remained of the ancient Dome that had been throne room to the sons of Elendil.