San Carlo alle Quattro Fontane

A small church built by Francesco Borromini between 1638 and 1641 on a corner of the Quirinal in Rome, his first independent commission. Barely 20 metres long (the whole nave would fit inside one of the piers of St Peter’s), it has an oval plan that waves in and out as nobody had dared before, and an oval dome patterned with crosses, hexagons and octagons that shrink towards the centre to fake extra height. Borromini’s Baroque starts here, in the work of Bernini’s great rival.