The parish church of San Julián and Santa Basilisa of Isla is one of the most beautiful examples of a colonnaded hall church in Cantabria. Its three naves, each with four bays, have considerable height, with the central nave being wider, giving it a cathedral-like appearance.
In 2002 it was declared an Asset of Cultural Interest in the monument category.
Special mention should be made of the bell tower, which rises at the foot of the church and, with its considerable height, displays the grandeur and distinctive layout of the well-known Trasmiera towers.
We could say that this church is one of the clearest examples of classical architecture in Cantabria, which preserves the hall church plan model throughout the 17th century.
Inside, the main altarpiece stands out: an impressive 17th-century polychrome altarpiece, with great decorative richness and considerable proportions. The reliefs depicting scenes from the life of the Virgin stand out, and in the predella are the themes of the Last Supper, the Agony in the Garden and the Entry into Jerusalem.
Mention should also be made of the English romantic-style organ, unique in Cantabria, built around 1890, and likewise declared an Asset of Cultural Interest in the movable category.
