Mediaeval monastery of Santa Maria de Alcobaça is located in the Central part of the city of Alcobaça. The city received this name in honor of the rivers Alcoa and Bass, at the confluence of which it is located.

The monastery was founded by the first king of Portugal, Afonso Henriques, in 1153. The Church and monastery were the first buildings in Portugal, built in the Gothic style, and are considered important historical monuments of the middle ages. In 1989 UNESCO included the monastery of Santa Maria de Alcobaça in the list of world heritage sites.

The monastery was one of the first churches of the monastic order of the Cistercians in Portugal and was built by the king of Portugal Afonso the Navigator in honor of his victory over the Moors. The construction of the monastery was part of the strategy of the king, who wanted to strengthen his authority in the newly established Empire and to facilitate the colonization of land recently reclaimed from the Moors.

At the time of construction of the monastery, in 1178, the monks of the order of Cistercians had already been in town for over 25 years. All this time they lived in wooden houses, and in the monastery moved to 1223. The Church was completed much later and is considered the largest Church in Portugal. The final touch to this ensemble is a covered gallery Silencio (gallery of Silence) in the Gothic style, which was built in the XIII century.

Library of Alcobaça is one of the largest libraries of the middle ages in Portugal. In 1810, during the French invasion many books were stolen. The remainder of the books are now kept in the National library of Lisbon.

During the reign of king Manuel I, was added a second floor above a covered gallery Silencio and built the sacristy in the Manueline style. The monastery was further expanded in the eighteenth century by the construction of a new indoor galleries and towers of the Church, was updated facade in the Baroque spirit. Inside the Church are the tombs of Dom Pedro I and Dona Inês de Castro, built in the Gothic style, and which are excellent examples of Portuguese art of the fourteenth century.