The Silmarillion

The First War is fought before Arda was “full-shaped” (12). Tulkas chases Melkor away and, once the war was finished, the Valar continue to shape everything. They plant forests and fashion the sun and the moon. Once the Valar are happy with their work, Manwë makes a great feast. While the Valar are tired, Melkor gathers his forces. He sneaks into Middle-earth while Tulkas sleeps, unseen by the Valar. Melkor builds a vast underground fortress named Utumno, and his presence begins to poison the land. When the Valar investigate, Melkor launches an attack that destroys the perfect balance the Valar had created in Arda. Then, Melkor flees to Utumno.

After the destruction, the Valar have no place to live in Arda. They retreat from Middle-earth to the Land of Aman in the west and turn it into a fortress of their own. They build mountains, the highest of which is Amon Uilos, where Manwë places his throne. The land is blessed, free from “any corruption or sickness in anything that lived” (14). They also build a city named Valmar. There, Yavanna grows the Two Trees of Valinor, whose daily blossoming creates the Count of Time (i.e., the passage of time).