In Akçakale, which 18 km . to the west of Trabzon, there is a fortress built on a terrace facing the sea. It is estimated that the fortress was built by emperor Alexius I (1297-1330) for protection against the Seljuks. The fortress was defended for another seven years after the conquest of Trabzon, until it was taken over by Mahmut Pasa, one of the commanderes of Fatih Sultan Mehmet. When he died during the attacks, he was buried at the fortress. This fortress, reconstructed in the Ottoman time and enlarged by additions, served as an important military base until the beginning of our century. Although most of the fortress has collapsed, the original style can stili be made out. However, the sections between the storeys made of wood, did not reach our time.

            THE ARSENAL
This is perhaps the striking and controversial of all Trabzon 's buildings. In the illustration in the Yildiz Palace Albums it has been daded H. 1305 and the monogram of Abdülhamit II and inscription corroborate this assumption. Thus, its construction date can be definitely confirmed as 1887. 
This structure comprises to circular buildings one inside the other, the radius of one being 25m. and other, 40m. The inner structure is fuor storeyed and outer, thee storeyed. Both the inner and outer structures have 13 windows surmounted by oval arches. The whole is surrounded by a high protective wall and there is a guardroom on its west side. During the Russian invasion of 1916-1918 it was used as an Arsenal and the roof was blown off by an explosion which took place on 9 July, 1919 .

            TRABZON CASTLE
The city walls, the greater part of which are still standing, are among the city's oldest structures. Indeed, their oldest part can be daded back to the 5st century AD, that is the Roman Period. Historical sources provide information about older stages of their construction. Xenophon, who visit the city in the 5th century BC, also mentions the existence of city walls.
The walls of Trabzon can be divided into three parts that is Yukari Hisar (The inner stronghold). Yukari Hisar and Orta Hisar were founded on the towering mass of rocks between Kuzgun Creek and Imaret (Iskeleboz) Creek. This structure comprises the oldest part of the stronghold and could be described has roughly Trapezoid in shape.
The name of the city derives from the word “Trapez” or “Trapezus”, which means “Trapezoid”.