The historic core of the city once was entirely enclosed in walls, the course of which remains visible today only in their remnants. In the 13th century, with the fall of the city and its environs to Venice, the walls were erected it is generally believed on the remains of Late Antique fortifications. They were the work of local master builders, which, in lengthy and persistent labour, at first constructed low defensive fortifications, and later, in their traditional manner, erected high walls with the characteristic battlements, made of cut quarrystone. The walls were renewed repeatedly. An older square tower stands next to the former city gate, while the round towers stem from the Renaissance. The latest restoration works on wall fragments lining Prolaz Venecija and the seashore side of the Brolo Park were carried out in 2004/05.