One of Livorno's great landmarks is the beautiful fortress that dominates the town's harbour. Dating back to the Middle Ages, the fortress started life as a tower, but over the years more has been built around it. The aim, of course, has been to protect the important hub that Livorno was and to some extent still is today. Today, the characteristic square tower stands, considerably lower than then, though still visible above the fortress walls. Immediately next to the fortress stands a round tower, Mastio di Matilde, built somewhat later than the original tower.