This Moslem, Calif-style fortress was built in the X century to defend the lands of the Duero from Christian attacks during the Reconquest.Built with ashlar carved stone.Divided into two areas by a moat:the fortress and the walled enclosure where the soldiers and the cisterns were.In the fortress there were seven towers out of which the Almanzor and the Keep are the most noteworthy.It also had an underground reservoir and an important armoury.This castle is mentioned in the “Cantar de Mío Cid”. El Cid Campeador was mayor of the fortress once taken by the Christians.It is the longest fortification in Europe.