Gaziantep Castle stands on a basalt mound in the old city centre, the fortified core of a settlement that has been continuously inhabited for over five thousand years. The current structure is primarily Byzantine and Mamluk in origin, though it incorporates elements from every major power that has controlled the city. The circular keep with its thick walls and arrow slits gives a good sense of medieval military architecture.
The castle houses a small museum documenting the 1921 Battle of Gaziantep, when the Turkish resistance held the city against French forces for nearly a year. The rooftops offer panoramic views over the city and the surrounding plain. The castle is best visited at dusk when the stone glows warm and the city below is lit up, and it is an easy walk from both the Zeugma Museum and the old bazaar district.