The Heptagonal Tower, standing on a small rise, was built in medieval times. Historical sources date the this defensive tower to the 12th century, although it most likely consists of overlapping wall sections from different phases that are difficult to distinguish. Together with the Clock Tower, it formed part of the castle’s defensive system, acting as a spur tower projected forward to absorb the main impact of attacks. According to another tradition, the tower dates back to the 5th century and may have given rise to the castle’s name, which is thought to originate around the 8th century. In the 16th century, the tower lost its defensive function and became a bell tower. For this purpose, four round-arched windows were opened in the upper part of the structure, while a small bell, dated 1524, was placed inside the belfry. The architectural complex, 25 m high, has a quadrangular plan, while the tower takes on a heptagonal shape. The structure was originally designed to support a terrace featuring a pinnacle or a spire roof, typical of Arab architecture, which was lost in the 1920s. At the top of the tower, an imposing Ghibelline battlements, supported by stone corbels, can still be seen today.
