Castillo de San Marcos de Sanlúcar de Guadiana Monument · Sanlúcar de Guadiana, El Andévalo, Huelva Fortress set high above the Guadiana, in the area conquered by Sancho II of Portugal in the 13th century, and a defensive bastion facing the Portuguese bank. siglo XIII Photo: © MiguelAngel fotografo (CC BY-SA 4.0) What to see and do in Sanlúcar de Guadiana