Gaziantep castle (Gaziantep kalesi, also called: the panorama museum) goes a long way back: most probably the Romans already had a first fortress on this rock, followed by the Byzantines, Arab rulers, Selcuk and Mongol rulers and whoever passed by in this region: the list of different rulers is long. Going to Gaziantep castle means having a perfect panorama over the city. It is nice and well enough restaured for a good impression what the castle was like in the old days.
Moreover this castle is used as the expression of Antep’s heroism. The people of Antep played a crucial role in the War of Indepences in 1920-1921 and were honoured by Mustafa Kemal Atatürk with the title ‘Gazi’: great, heroic. The war of indepence came after that the Osman emperor and its calliphate were defeated; Turkey was attacked from all sides, by the English, the French, the Armenians, the Greek, the Russians: they all wanted their share of the remains of Turkish territory. Under the leadership of Atatürk a war of independence started and they won. This is seen as the ultimate survival of Turkey – without this war, Turkey would no longer exist and Turks would not have a land of their own. Five or six thousand inhabitants of Antep lost their lives in that war but their role was decisive. The Gaziantep castle shows this history and the pride, the nationalism of this town. Lots of kids are visiting the castle to learn about the war but also many Turks from Gaziantep and elsewhere show indepth interest in the exposition.
All the written texts are in Turkish and English, the film is only in Turkish. If you want to understand the politics and national feelings of Turks in the past and the present, this is a must-go.
A disadvantage is that they feel the need to copy the fights. During the whole exposition, you will hear the sounds of guns and artillery; it can make you nervous and I do not see the purpose it serves. But apart from that, I’d recommend a visit. It is another, however non-critical example of how people interprete and write their history (see my blog about the Stockholm Museum), in relation to the actual context.
More on this subject: the War Museum (Savas Müzesi) in Gaziantep

Other short info about the castle: https://www.alaturkaturkey.com/destinations/gaziantep-castle.html

A blog about another nearby interesting site to visit:
A kastel is not a castle in Gaziantep