For many people, the highlight of their visit to Dubrovnik is walking a circuit of the battlements atop the monumental medieval walls. The complete circuit runs 2km (1 1/4-mile) around the perimeter of the Old Town, affording ever-changing vistas over the terracotta rooftops and out across the glittering blue Adriatic. In places the walls are up to 25m (82-ft.) high and 6m (18-ft.) thick, combining several sturdy fortresses and proud towers along the way. You should allow at least 1 hr. to complete the walk, though it may well take longer should you be captivated by the endless photo opportunities on offer here. There are three main points of access up to the walls: just inside the Pile Gate, near the Maritime Museum, and near the Dominican Monastery at the Ploče Gate. To start your walk at Pile Gate, you should turn left immediately as you enter the Old Town and walk up a steep flight of stairs topped by an arch. From here you will proceed in a clockwise direction. The walls date back to the 13th century, but were heavily reinforced during the 15th century due to fear of attack by the Ottoman Turks.