Amon Gwareth
From Tolkien Gateway
Amon Gwareth (S. amon "hill" + gwareth "watching") was the hill that stood in the valley of Tumladen, within the Encircling Mountains, on which Turgon built the city of Gondolin.
Etymology
Christopher Tolkien says that his father later changed the name to Amon Gwared but this change did not make it in the published Silmarillion.