Arraiolos Castle is a medieval stronghold classified as a national monument. The fortress was built on a rocky hill at the beginning of the 13th century. Its construction was commissioned by the Portuguese king Afons II.
The medieval defensive castle was built on a circular plan on the Monte de S. Pedro hill. The Romanesque-Gothic stronghold changed its owners over the years, belonging among others to Ferdinand I of Burgundy and Nuno Álvares Pereira. In the 17th century, despite a thorough reconstruction, the castle was abandoned and it began to fall into ruin.
Among the historical walls of the castle of Arraiolos is, among others, the 16th-century church Igreja do Salvador. The location provides beautiful views of the village of Arraiolos and surrounding villages. The castle remains one of the few in the world with a round structure.