The citadel and the walls of Diyarbakir is situated 100 m. above the valley of River Tigris. Diyarbakir still carries e mediavel atmosphere with its walls encircling the city. Although there were Roman and probably earlier walls here, the present walls date back to early Byzantine times. There are sixteen keeps and five gates, each of which deserve seeing along with their inscriptions and reliefs. There are four main gates along the wall called as Dag Kapi, Urfa Kapi, Mardin Kapi and Yeni Kapi. The black basalt walls are perfect examples of the military architecture of the Middle Ages. The walls today are 10-12 m high and 3-5 m thick.