Amon Gwareth
the Hill of Watch; the hill in Tumladen whereon Gondolin stood
Names
Amon Gwareth — “the Hill of Watch” — the hill in the valley of Tumladen where the hidden city was set.
Geography
Amon Gwareth rose in the centre of the hidden vale of Tumladen, which the Encircling Mountains (the Echoriath) walled about on every side. It was a hill of green turf in the midst of the green plain, and its summit dominated the valley; from afar within the vale its height was the first landmark of the land.
History
When Turgon came by the hidden way into Tumladen he built upon Amon Gwareth the city that was hidden from all eyes but the Sun and Moon — Gondolin, the fairest of the cities of that age. The hill bore the towers of the city until the day of the sack, when Gondolin was betrayed and overthrown, and its ruin was complete with the fall of Beleriand.