The place of council and judgment of the Valar, outside the gates of Valmar, and bathed in the light of the Two Trees of Valinor. The thrones of the Valar were set there.

The Valar were at Máhanaxar on several occasions - the creation of the Two Trees of Valinor, before the War against Melkor, when Melkor was brought back in chains, when Fëanor was summoned before the Valar, and after the flight of Melkor.
Encyclopedia entry originally written by Ereinion