The kastra (castle) encloses Byzantine churches and timber-framed houses with overhanging upper storeys. Enjoy panoramic views from the tower by the eastern edge of the Byzantine Walls, built to survive sieges in the late 4th century BC. Emperor Theodosius fortified the walls; in places they were 10m high and 5m thick. They stood until the 19th century when the Ottomans demolished large stretches. Enjoy the views of the sunset over the city, along with students and locals.