A replacement for an older Byzantine edifice, the city’s famous Tower was built in the late 15th century on alluvial soil at the confluence of the city’s eastern and sea walls. It is a cylindrical building standing at 33.90 meters, whose cannons defended the city and the Thermaic Gulf. An octagonal mantle wall which had been added was subsequently demolished in 1911. The Tower’s purpose was primarily defensive, though it also functioned as a military barracks In 1688, the Flemish writer and geographer Olfert Dapper, having never visited, described it as the city's smaller fort on the dock, which extended towards the sea and was equipped with five cannons.