San Carlo alle Quattro Fontane: Borromini's masterpiece

Updated on October 5, 2026

The church of San Carlo alle Quattro Fontane (nicknamed "San Carlino"), at the crossing of via del Quirinale and via delle Quattro Fontane, was the first major commission of the architect Francesco Borromini. Built from 1634 for the Spanish Trinitarians, it is tiny: a Roman tradition says it would fit inside one of the piers of St Peter's. Its oval coffered dome, undulating façade and small octagonal cloister make it one of the high points of Baroque architecture. Entry is free and the visit takes 20 to 30 minutes. The opening hours come from the community's website and secondary sources: check them before you go.

Highlights

The interior and the dome

Borromini built the plan from simple geometric shapes, so the walls undulate. Above, the oval dome with coffers of varied shapes (octagons, crosses, hexagons) shrinks towards the lantern, which lets in the light: this gives height to a minuscule space. Sit on a bench, then look up.

The façade

Completed in 1665-1667, near the end of Borromini's life, it alternates concave and convex curves on two levels. Look at it from the opposite pavement.

The cloister

Designed in 1635-1636, this cloister with an octagonal plan and convex corners, on two levels, is a model of harmony and proportion. You visit it with the church during opening hours.

The crypt

To the left of the entrance, behind a gate, the crypt follows the plan of the church and holds two chapels, one of which was meant for Borromini's tomb.

The Four Fountains

The four corner fountains at the crossing, which give the church its name, represent the Tiber, the Arno, Diana and Juno.

Practical info

Tips

Free entry; a donation for upkeep is appreciated. No reservation for individual visitors; the church holds only about forty people at a time, so there may be a wait. Mass on Sundays and feast days at 11am. Audio guides are available on smartphone. Modest dress required. To place the church within the work of Borromini and Bernini, read Baroque Rome: in the footsteps of Bernini and Borromini.

How to get there

Via del Quirinale 23, 00187 Rome. Metro line A, Barberini station, 7 to 8 minutes' walk. The church is a few minutes' walk from the Palazzo Barberini and 10 minutes from the Trevi Fountain.