Erected over a simple hermitage dedicated to S. Bento, built in 1169, the Cistercian monastery of São Bento de Cástris, one of the oldest female religious houses in Portugal dates back to the 14th century, having been consecrated in the year 1328. The current temple shows traces of the Romanesque, Gothic, Mudejar, Manueline and Baroque heritage; however the main interventions occurred in the reign of D. Manuel, a period in which it was substantially altered under the aegis of the noble House of Almeidas. The construction is arranged around a central cloister, being the entrance to the conventual premises made through a portico topped by a triangular pediment and thin pinnacles, having engraved in the center, the ecclesiastical arms of S. Bernardo de Claraval flanked by two niches, currently empty and originally destined to the patrons of the Cistercian Order, S. Bernardo and S. Bento. This passage communicates with a large patio that opens onto the main facade of the temple -to the South- and to the remaining two facilities - to the North- respectively, house the Curator and House of the Confessor. The main façade of the convent, structured in two registers, is torn by rectangular windows and two porticoes: one, a perfect rounded arch of stonework, and the other a downed arch supported by staves in rusticated stonework, with the date 1617 engraved on the lintel, giving access to the area of the old orchard. Outside the temple and the sacristy two bells adorn the finish of the facade. The interior of the temple whose stylistic features are markedly Manueline, presents an axial entrance, located to the east which opens to a porch, torn by a portico of two archivolts, and finely turned columns, with braided bases, analogous to the portico, of the Royal Church of S. Francisco. The church, which has a longitudinal design, is divided into four sections, a high choir, covered by a ribbed vault with carved finials, some representing the armillary sphere, others the arms of the Almeida family. This type of vault goes beyond the church space, and can also be found in a gallery accessing the cloister. Frescoes still exist on the walls of some vaults, in the form of delicate polychrome representations of angels.