Capital of an ancient kingdom in the Muslim taifa, the castle of Tortosa stands guard from on high over the strategic crossroads between the Roman Via Augusta and the Ebro river.

Restored in modern times and adapted for use as a Parador hotel, it was an important fortress in Muslim times and in the subsequent Christian period. It was founded in 944, and the elements still surviving from the original Arab structure include the perimeter walls, which follow the design of the hill on which it stands, and is reinforced by square towers and by the circular tower of Túbal or Diamant, which stands on a rocky spur at the front of the city.
It also has several different arches giving access to the enclosure and various buildings (the arsenal, bailey, underground galleries, silos and a central well) which date mainly from the period of Gothic reforms in the 14th century, when it was in use as a royal palace. It marked the start of the medieval city walls, of which some sections and gateways –such as the Remolins gateway (14th century)– can still be seen today.