The Monastery of Serra do Pilar was created after the reform of the Order of Augustinians, when the monks of the monastery of Grijó were transferred to the new location. Construction of this new monastery began in 1537, which features a plan consisting of the church, circular in plan, the chancel, rectangular in plan, and the cloister, also circular in plan, all arranged sequentially. It is considered one of the most notable buildings of classical European architecture due to its circular church and cloister. In 1809 the space of the monastery was occupied by Wellington's troops, when the Portuguese army's attack on the city of Porto, then occupied by Napoleon's troops, was planned. During the 20th century, the monastery was the object of several conservation and restoration campaigns and is included in the Historic Center of Porto, inscribed by Unesco on the World Heritage List.