Erebor
When Imrahil declined to send the entirety of Gondor's army against Mordor, Aragorn led a smaller army to the Black Gate of Mordor to distract Sauron from Frodo's quest. The hobbits succeeded, and with Sauron defeated, the war and the Third Age ended. The Great Gate was rebuilt with "mithril" and steel by Gimli and Dwarves from the Lonely Mountain. Aragorn's coronation was held on the Gateway, where he was pronounced King Elessar of both Gondor and Arnor, the sister kingdom in the north.