OsgiliathOsgiliath - Before the White City became the glory of Gondor, Osgilaith was the capital of the realm.  It was only after it was assaulted by Sauron that it had to be abandoned and the exiles made the western tower their new home.

 

"The chief city of the southern realm was Osgiliath, through the midst of which the Great River flowed; and the Númenóreans built there a great bridge, upon which there were towers and houses of stone wonderful for behold, and tall ships came up out of the sea to the quays of the city.  Other strong places they built also upon either hand; Minas Ithil, the Tower of the Rising Moon, eastward upon the shoulder of the Mountains of Shadow as a threat to Mordor; and to the westward Minas Anor, Tower of the Setting Sun, at the feet of Mount Mindolluin, as a shield against the men of the dales.  In Minas Ithil was the house of Isildur, and in Minas Anor was the house of Anárion, but they shared the realm between them and their thrones were set side by side in the Great Hall of Osgiliath.  These were the chief dwellings of the Númenóreans in Gondor..." ~The Silmarillion (Of the Rings of Power and the Third Age)