Castillo de Vispieres

The castle of Vispieres, as it is commonly known, is in reality a 11x12 meter enclosure, built on the remains of a Roman fortress that served as a lookout over the Via de Agrippa. The Roman fortification may have been built on the site of a Cántabro castle mentioned by Plinio el Viejo in his Natural History. The medieval fortification was bequeathed by Alfonso XI of Castille to his son Tello in the 14th century and was later the property of the marquesses of Santillana, who were owners of other titles including the duke of Infantado. Only the walls of the castle, which are the remains of the medieval construction, are still standing today, according to the Diccionario geográfico-estadístico de España y Portugal of 1827.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons