Remains of 3 fortifications: one Roman, one Moorish and one medieval. Even those less interested in archaeology should not miss the Castillo on their visit to Medina Sidonia, as they can enjoy a fantastic view from there.
es.wikipedia.org/wiki/Castillo_de_Medina-Sidonia
The castle of Medina is a historical curiosity: remains of three temporarily superimposed fortifications were found here: Roman, Arab and medieval. It is also a spectacular viewpoint.