‘Hisar Kapısı’ (= Gate of the Fortress) is one of the two gates in the first (or outer) walls of the Ankara Citadel. Byzantine, 9th century AD (but restored a lot of times, even recently).
Both gates are flanked by semi-cylindric towers. This one lies less than 100 m north of the Archaeology Museum (or: ‘Hittit Museum’); on the tower to its left (not visible on this picture), stands a clock tower.

Correspondent: J.M.Criel, Antwerpen
Source: ‘Guides Bleus: Turquie’ – Edition 1986.