Máhanaxar, also called Rithil-Anamo, was the Ring of Doom, probably a hall or court where the Valar held their councils.
Other version of the legendarium
In the Later Quenta Silmarillion, as Melkor came through Aman and filled it with darkness and dread, he entered the Ring of Doom and cursed it, defiling Manwë's seat of judgement and casting down the thrones of the other Valar.
Description
Máhanaxar , also called Rithil-Anamo , was the Ring of Doom , probably a hall or court where the Valar held their councils.
The Ring of Doom was located outside the golden western gates of the city of Valimar with the thrones of the Valar that were arranged in circle. The evergreen hill of Ezellohar, upon which Two Trees of Valinor grew until its Darkening, laid within the Ring.
The Valar were sitting on their thrones while watching Yavanna chanting, bringing the Two Trees to life upon Ezellohar. Ever after, the Powers sat bathed in the light of the Trees to hold their great councils, and here some of the most momentous decisions of Eä's history were made.