The church of San Martín of Frómista is considered the purest Romanesque architectural work in Castile. It marks a climax in this particular style, on account of its perfect ordinance and the balance between the construction itself and the sculptural ornamentation. Dating back to the 11 C, this small church has a floor plan consisting of three naves, the central being wider and higher, a transept with a cupola on the centre, and three semicircular apses, the central being the largest.
The portals project outside and are covered by eaves supported by corbels. The cornices set on the corbels are richly carved with animal heads, plant motifs and busts or human figures in different postures. The transept, in line with the rest of the church, is remarkable for its octagonal cupola set over squinches and surmounted by a dome. On the west façade two semicircular twin towers rise at the corners.
Inside, the three naves of the temple are divided into five sections, four of equal dimensions, and the fifth one, wider, is the transept. The naves are covered by barrel vaults, shorter and narrower on the side naves; and end in semicircular archs.
With respect to ornamentation, the varied decoration on the capitals is worthy of note. There are many plant motifs: capitals with balls or cones that come out of big leaves, that end in scrolls on the upper side; capitals with winding stems that include leaves; and capitals with acanthus leaves. Some capitals are decorated with animal figures: a first line of human figures or others riding on animals, birds mixed with human figures.
Some of the historiated capitals do not offer an easy interpretation. Among the most outstanding are the scenes of the greedy; men carrying a barrel; men fighting; Adam and Eve and other scenes from the Old and New Testaments. Some other are based on old models. There are many sculptures decorating the corbels, that show the artist´s talent for representing the anatomy and postures of the characters.