MÉRTOLA, 54km southeast of Beja, is as beautifully sited as any town in the south, set high on a spur above the confluence of the Guadiana and Oeiras rivers, guarded by the ruins of a Moorish frontier castle. It makes a fine place to stay the night, or longer, with a compact, somnolent old town full of attractions, and quiet rural surroundings that form part of the Parque Natural Vale do Guadiana. The region is home to the rare black stork and other endangered species, and the local hills, riverbanks and valleys have some excellent walks, especially round the old mining village of São Domingos.

Mértola’s history goes back as far as Phoenician times, when it was an important river port, and it was later fortified and expanded by both Romans (as Myrtilis) and Moors (Martulah), before being taken by Dom Sancho II in 1238 as part of the Christian Reconquest. With the walled town occupying such a small area, successive conquerors and settlers simply built on what they found, which provides Mértola with its current fascination – the evidence of thousands of years of habitation visible in almost every building and street.