The castle of Monforte is situated in what was the former local council of Monforte de Rio Libre, and was built over the remains of a hill-fort in the twelfth century. Destroyed during the wars against León, it was rebuilt by Afonso III, who granted the walled fortifications a charter, transforming it into a town.

It belonged to Prince Francisco, the brother of King João V, and was finally abandoned in 1853 when the local council ceased to exist.