Crafted between 1490 and 1503, it naturally belonged to the previous temple. It is a splendid combination of 20 panels painted in tempera and 57 polychrome wood carvings. Noble woods are used: cypress, walnut, cherry, and pine from Flanders. The design of the altarpiece is Gothic. Its structure is formed by a large bench, a main body with five lanes and three different levels and a dustcover that provides a frame. The tabernacle showcase stands out, a fine piece of craftsmanship in polychrome wood of Gothic-Mudejar design, which serves as a pedestal for the central carved sculpture of The Virgin of the Assumption, with distinctly Flemish features. The carving and ornamentation of the altarpiece are the work of the Flemish master, Gil de Brabante, a resident of Huesca, who followed the model for carving proposed by the so-called school of Brussels. But what is truly outstanding in this altarpiece are the marvellous pictures painted by the "MAESTRO DE BOLEA" (Master of Bolea), an anonymous painter that, still in the time of the Gothic period in Spain, uses stylistic devices uniting two trends:
Flemish style, because of the extremely accurate resolution of the concept of space, the display of feelings in the peoples' expressions, the detailed representation of nature in the plants and bushes and the completely original richness of colour, with the wide range of reds and greens standing out.
Italian style, from the Quattrocento period, showing perspective, light and shade in an innovative way for Aragon. The style of the Maestro de Bolea is linked to the work of Juan de Borgoña and Pedro Berruguete.