Which church in Rome has an oval dome designed by Borromini?

San Carlo alle Quattro Fontane is the Roman church with an oval dome designed by Francesco Borromini.

Also known as San Carlino, the church was Borromini’s first major independent commission. He designed it in the 1630s for the Spanish Trinitarians, an order dedicated to redeeming Christians held in slavery. The project occupied a difficult, sharply constrained corner site on Rome’s Quirinal Hill.

Borromini created an extraordinarily compact interior from interlocking geometric forms. The walls curve inward and outward, while the plan and dome draw on ovals, crosses, hexagons and octagons. Smaller geometric patterns rise toward the lantern, creating movement and visual depth despite the church’s small size.

The church was built between 1638 and 1641 and dedicated in 1646. The unfinished upper portion of its façade was completed after Borromini’s death. The nearby Sant’Andrea al Quirinale, with an oval church plan, is a frequent source of confusion, but it was designed by Bernini.