Museo de la Tortura is a grim little museum in the old centre of Santillana del Mar, a short walk from the village's stone lanes and Romanesque collegiate church. Its collection focuses on torture and capital punishment devices used in Europe from the late medieval period into the early modern age, with iron collars, cages, racks, masks, and execution tools arranged in a sequence of small rooms.
This is not a museum for everyone, and it can feel more macabre than scholarly. Still, it gives a sharp, uncomfortable counterpoint to Santillana's postcard prettiness, especially if you have already seen the Altamira museum and the town's religious architecture. Go in expecting a compact historical curiosity rather than a polished national museum, and skip it if displays of punishment instruments are not your idea of travel.