Isolated from the rest of the ramparts since the destruction of the maritime façade (1866), the town's most famous monument dominates the seafront with its imposing and austere-looking mass. Built by the Ottomans (15C), this round tower - 23m in diameter and 34m tall - was a prison in the 18C. After the 1826 massacre of the Janissaries it became known as the "Bloody Tower". It houses the rather poorly stocked Museum of the History of Thessaloniki. Superb panoramic view from the top.