This huge basalt citadel (3C, remodelled in the 13C and 15C) stands in the heart of Kayseri. Its belligerent appearance, blocks of lava and 19 towers dotted around the rampart walk make it one of the most impressive examples of medieval architecture in Turkey. Cunning defensive systems were developed here, such as the 30m-long barbican placed between an external double gate and a watchtower.