Which Baroque architect designed the Church of San Carlo alle Quattro Fontane?

Francesco Borromini designed the Church of San Carlo alle Quattro Fontane in Rome. Commonly called San Carlino, it was his first independent architectural commission and became a defining achievement of the Roman Baroque.

The church was built for the Spanish Trinitarians, a religious order associated with freeing Christian captives. Borromini worked within a very cramped, irregular site near four street-corner fountains, using an inventive plan of curves, ovals, and geometric forms instead of a straightforward rectangle.

Inside, sixteen columns organize an undulating lower space that rises toward an oval dome. The dome’s coffering uses diminishing octagons, crosses, and hexagons, while carefully arranged windows create a hierarchy of light from the bright lantern down into the darker church interior.

Borromini’s church is often contrasted with Bernini’s nearby Sant’Andrea al Quirinale. Both architects shaped seventeenth-century Rome, but Borromini became especially known for restless geometry and spatial complexity. Construction of San Carlo began in 1638, and the church was dedicated in 1646; parts of the façade were completed later.