Hilltop Castle (Castelo)

The castle of Mértola sits on the highest point of the town, on a rocky spur above the meeting of the Oeiras and the Guadiana, and it dominates the roofs of the white houses and the plain beyond. The position makes strategic sense. The Guadiana is navigable up to this point from the sea, so a fortress here controlled river traffic and a long stretch of the surrounding country. The hill has been occupied for a very long time, and the town's history reaches back through Roman Myrtilis and earlier trading contacts with Phoenician and other Mediterranean merchants, followed by Visigothic and Muslim periods.

The present castle dates mainly from the 13th century. Mértola was taken from the Muslims in 1238 by Paio Peres Correia, master of the Order of Santiago, who was given the town and strengthened its defences. The walls and towers of this period, built of local schist, still stand. The keep, a tall square tower, is the dominant feature and can be climbed for a view over the town, the river, and the empty hills of the Baixo Alentejo. Parts of the walls are built on earlier foundations, and some of the stonework reveals reused Roman material, a reminder of the layers beneath.

Inside the walls, a courtyard and a series of stairways and ramparts allow a walk around the circuit. The setting is simple and the atmosphere is calm, with few visitors even in season. From the battlements you can look down on the former mosque, now the parish church, and the old streets running down to the river, and in the distance see the road and the bridge. At sunset the stone takes a warm glow and the town below turns gold.

The climb from the centre is steep but short, along cobbled lanes. Wear shoes with good grip, and bring water in summer, since the Alentejo can be very hot and there is little shade on the walls. Opening hours are set locally and may change, with a lunch break, so check before going.

The castle suits history lovers, photographers, and travellers exploring the quiet lower Guadiana. A visit takes around an hour and works well in combination with the town's museums and a walk by the river.