The present military fortification at the Turó de la Seu Vella was built between the 17th and 20th centuries, although most of the defensive structures were built during the Catalan Revolt and the War of Spanish Succession. The fortification is configured in a quadrangular enclosure located at the highest part of the hill. A powerful bastion dominates each of its vertices.  The fortification is completed with other bastions and counter bastions, walls, tunnels and walkways.