This fortified castle built with red sandstone was destroyed by the 1755 earthquake. The high walls, which have been partly restored, shelter the ruins of an early 12C castle. The path round offers a panoramic view over the small town centre and fort of São Sébastião, the salt marshes, the Guardiana, the bridge which joins Portugal to Spain, Ayamonte in the east, Villa Real de Santo Antonio and the coast in the south.