Castle of San Martín Monument · Soto del Barco, Avilés, Asturias San Martín Castle, in the Asturian concejo of Soto del Barco, was built or rebuilt on a Roman fortress that in turn stood on an ancient castro, with occupation layers from the first and second Iron Age, the Roman period and the early Middle Ages; it is on these latter layers that the castle now stands, first recorded in the 11th century and restored in the late 15th. The site was excavated in the 1990s, although the results of those campaigns were never published. The tower is surrounded by a wall reaching the bank of the Nalón river, which in other periods included structures such as the church of San Martín; also preserved nearby are 19th-century buildings, among them a house with a cantilevered glazed gallery. Photo: José Antonio Gil Martínez from Vigo, Spain (CC BY 2.0) What to see and do in Soto del Barco