The church of San Juan de Mercado is built in style Romanesque of the 12th century
The plant of 62 m long x 24 m wide is three-nave basilica type surmounted by semicircular apses. The church has the usual liturgical orientation, with a slight deviation, NE 65th. In the construction of the temple in its early Romanesque sandstone was used ax stonemason carved and properly squared.
Stresses the high number of quarry marks both outside and inside the temple, approx. 250 of 35 different types, some rare. They focus on the south façade, apse and columns of the nave of the Epistle.