This Monastery is crucial to understand the architecture of the Romanesque of the Tâmega and Sousa, not only for its unique architectural and sculptural features, but also due to the fact that this former Benedictine Monastery shelters the tomb of Egas Moniz, one of the key figures of the beginning of Nationality.
The Monastery is a standard-building for the region, visible in its very own decorative style, both in its themes and the sculptural techniques applied.
These value the prismatic columns in the portals, bulb-like bases, resorting to bevelled botanic decorative patterns, developing long friezes inside and outside the church, much in the style of the architecture of the Visigoth and Mozarabic period.
Despite its Romanesque features, the Monastery was built in the 13th century, featuring shares of various periods, including elements that were reused from an older construction, probably from the second half of the 12th century, and others of clear Pre-Romanesque nature which have inspired the artists working in the 13th century workshop.
Built with three naves, a false transept designed in the plan, and wood roofings based on diaphragm arches, the Monastery still features a chevet consisting of three intercommunicating chapels.
Two of these, the lateral ones, are semicircular in the Romanesque style and the central one, with a rectangular plan, is the result of changes made in the Modern Period.
A new building arises on the west side, developed on the basis of the pre-existing church, highlighting a first construction phase in the first flight and axial portal to the west, whose elements, including capitals and corbels, some inspired in the Coimbra tradition, the other in the See of Porto, among other sources, correspond to the earliest moment.
The second phase is represented by the south portal, less archaic than the one to the west, and the contrast between the flights, these being tighter and lower than those of the first phase.
In the third phase, the apses of semicircular plant covered by a broken barrel vault stand out for being quite modern elements within the Romanesque style.
In the last phase of construction of the Monastery, reference should be made to the roofing of the transept and the tower over the cross, whose late architecture resembles the mendicant Gothic.
In the portion of the wall of the transept to the north, friezes and lines of ashlars prior to the 13th century construction were integrated, namely in the crevice of the apses, in the frames and some capitals, as the one in the apse to the south, which present a Mozarabic style.
The proto or pre-Romanesque elements and revival, such as the friezes bevelled with botanic decoration, which extend along the walls, both inside and outside, result from the inspiration on the motifs and profiles of the pre-Romanesque lines of ashlars.
Similarly, the diaphragms-arches used in the naves are an element that recalls the spatiality of peninsular pre-Romanesque churches.
Inside the Monastery there are some elements that result from the reform which took place during the Modern Period, namely the space of the chancel, once narrow and deep, underwent several restoration works.
The altarpiece of the main altar shows a design and decor of rather late chronology within the Modern period, with a mixture of the rococo and the emerging neoclassic.
The cloister and the remains of the Monastery building are clearly a result of the reforms of the 17th and 18th centuries.