Above the parish church looms Mértola’s fortified castle, most of which dates from the 13th century. It was built upon Moorish foundations next to an Islamic residence, the alcáçova (citadel), which itself overlaid the Roman forum. For centuries the castle was considered western Iberia’s most impregnable fortress. From the walls, there are ultrafabulous views – the alcáçova is on one side, and the old town and the river on the other.

The castle’s prominent tower, the Torre de Menagem, has exhibitions related to the history of Mértola, with several worthwhile (if dramatically scored) videos in both English and Portuguese on Mértola’s strategic location and the reconquest by the Knights of Santiago in 1238.