It is a late Romanesque building built in ashlar, begun at the end of the 12th or beginning of the 13th century. It consists of a nave with three bays and a presbytery, both rectangular and covered with a pointed barrel vault, separated from the apse by a triumphal arch supported by a belfry with two bays. The apse is semicircular, narrower and covered with a pointed quarter-sphere vault.
The complex must have been built in two stages, as different hands can be seen: the chevet up to the triumphal arch must have been built between the 12th and 13th centuries by a good craftsman with knowledge of both architecture and sculpture, as he introduced historical themes; the nave and the belfry were perhaps built in the mid-13th century by a less skilled stonemason with no notions of sculpture, as he only sculpted plant motifs.
The apse has three semicircular windows. They are decorated with different geometric motifs: diamond latticework, undulating lines, nail heads, blades, etc. ….. The capitals are decorated with pine cones, palmettes, a double-tailed fish-mermaid holding her two sea limbs in her hands, and two symmetrical birds facing each other and pecking at a tree trunk.
There are three half-columns that reinforce the apse vertically. One of the capitals is decorated with the symbolic theme of lust with a figure of a naked woman whose breasts are sucked by two snakes, which she holds in her hands. On either side she is tortured by two demons with the claws of birds of prey and the snouts of crocodiles. Another of the capitals presents a Pantocrator blessing and flanked by two Tetramorphs: to his right the winged man in an attitude of adoration (Saint Matthew) and to his left a bird that looks more like a peacock than an eagle (Saint John).
The corbels of the apse are also historiated, as they present human and animal busts, one of which is a carátula with an enormous open mouth sticking out its tongue and bristling hair, symbol of the devil.
There are decorated capitals on the triumphal arch: one with four male harpies facing each other two by two at the corners and another with the theme of the Epiphany.
There are two doorways in this church. The main one is the one that opens to the south, in an archaic Romanesque style. It has three semicircular archivolts, without capitals, and its only decoration is the garnish based on rosettes.
The secondary doorway, off-centre from the axis of the nave, an unusual location for a doorway in Romanesque La Rioja. It was blinded until its restoration in 1984. It is decorated with checkerboard motifs, vanes, zigzags and eight-petal rosettes.