Soon after Thessaloniki was founded in 315 BC, the town was surrounded by defensive walls to withstand attacks by King Pyrrhus of Epirus in 285 and by the Celts in 279.
Constantine the Great strengthened the fortifications, and under the Byzantine Empire, the walls were frequently enhanced. In the 14th and 15th centuries, the Turkish authorities built additional defensive structures and towers, often using Venetian military engineers for the construction.
