Large stretches of the ancient city walls remain visible, cleaving their way around the modern city. Originally 8km long, this defensive system was erected by the Byzantines from the 4C on foundations inherited from Cassandra and the Romans. It is almost the only example of Byzantine fortifications with some 60 towers, and the wall alternates stone and mortar with broad strips of brick. A walk that shows you a more down-to-earth side of Thessaloniki.