The citadel is located on a spot where already in Justinian times a fortress was erected. However, the present citadel owns its existence to the Seljuks, who took the city in 1071-1098. The oldest finds on the site date to the chalcolithic period (3700-3500 BC).
You will see some pictures of the building in the left lower corner, which is a well-preserved han. The mosque I forgot to visit.