Castillo de Sancho IV el Bravo Monument · Cumbres Mayores, Sierra de Huelva, Huelva Nine-sided fortress built in 1293 by privilege of Sancho IV, with 15th-century alterations, walls up to 10 metres high and 3 metres thick; declared Monumento Histórico-Artístico (Spain's heritage designation in force between 1931 and 1985) in 1973. 1293 (construcción); 1973 (declaración) Photo: Rodelar (CC BY-SA 4.0) What to see and do in Cumbres Mayores