Of all the things uncovered in the Aire e Candeeiros natural park over the years (stalactites, Roman cobblestones, dinosaur footprints), the oddest is surely salt – mined here since ancient times. It’s still produced near the town of Rio Maior, at the foot of the Serra dos Candeeiros, where a wide bed of concrete-lined salt pans (marinhas do sal) exploits the bed of rock salt under the local mountains. Workers at the cooperatively owned Salinas Naturais de Rio Maior pump salty water from a well and then subject it to various concentration and evaporation techniques in the tanks and pans on view. It’s a process that has been going on, in some shape or form, since the twelfth century. There’s most activity between June and September, but you can see something at most times of the year since many of the old wooden salt sheds have been turned into craft stores, salt shops and rustic taverns, and there are even a couple of restaurants where you’ll get a good grill-lunch with the salt workers. The sheds themselves are curious works, with weathered boards, gnarled olive-wood posts and ancient wooden locks. The salt pans lie 3km north of Rio Maior (off the IC2/N1), but signposting is patchy. Coming into the town centre, follow scant signs for “Marinhas do Sal” and “Salinas” (on the Alcobertas road); you’re there when you see the Wild West-style wooden buildings overlooking the salt-beds.