Building of the family of the so-called "Cistercian Romanesque", it introduced a new spatiality that in a certain way prepared the advent of the Gothic. The church was built between 1152-1169 by the "barbati" (brothers lay or converts, who could grow a beard, and who functioned as a highly qualified set of master builders mostly from France) and in which the Vitruvian scheme was applied "ad quadratum", in which the height of the central vault is equal to the total width of the temple. Some of the mosaics in the ruins of Conimbriga use this square-based geometry (Vitruvio, a Roman architect, found the ideal proportions for the human body, from which they were used as a metrical module for buildings). In this church, the French king's foot (about 0.325m) was adopted as a standard measure. The volumetric scheme of this church has a central nave covered by a broken cannon vault, which sits laterally in five transversal chapels, perpendicular to the central nave, each with its broken cannon vault, lower than that of the central nave. It is considered the oldest Cistercian foundation in Portugal.