An alcázar (see ) is a type of Moorish castle or palace in Spain and Portugal built during Muslim rule although the term is also used for many medieval castles built by Christians on earlier Roman, Visigothic or Moorish fortifications. Most of the alcázars were built between the 8th and 15th centuries. Many cities in Spain have an alcázar. The term is frequently used as a synonym for castillo or castle; palaces built by Christian rulers were also often called alcázars.