The Castle of Serpa is located in the historic centre of the town, at its highest point. The castle and the city walls dominate the surrounding Alentejo landscape and can be seen from a great distance.
The fortification of this site dates back to Roman times. It was later occupied by peoples from northern Europe and subsequently by the Muslims. Serpa was conquered from the Moors in 1166, and in 1295 King Dinis of Portugal ordered the construction of the walls around the town.
A curious and striking feature is the keep (Torre de Menagem), which was severely damaged by a massive gunpowder explosion when Serpa was besieged in the 18th century during the War of the Spanish Succession. The damage can still be seen today at the entrance to the castle.