Castle of Cea Monument · Cea, Sahagún, León Cea Castle stands on a hillock overlooking the town of Cea, beside the river of the same name, and dominated the line until the 13th century, when the border between León and Castile stopped running through this valley. The present building was built in the 15th century over an earlier castle, destroyed in the 12th century, which in turn stood on one from the 9th century, and this on a castro. It served as a prison for Navarrese kings and Castilian counts: around 1040 King Ferdinand I of León imprisoned his brother García Sánchez III of Navarre there. In the early 20th century it was used as a quarry for the village's new church, which caused its ruin, today reduced to a small tower and an arch of the wall; works in 2015 prevented its total collapse, and it can now be visited free of charge. Photo: Rodelar (CC BY-SA 4.0) What to see and do in Cea