San Carlo alle Quattro Fontane

Church · Quirinale (Quattro Fontane)Rome,Italy

A tiny Rome corner church whose white walls curve without a break, under an oval dome coffered to look far higher than it is.

San Carlo alle Quattro Fontane sits on a cramped street corner, on a plot so small that its awkward shape decided the whole design. A poor Spanish order bought the site in the 1630s and gave the job to Francesco Borromini, who was then unknown. He built them a church whose walls curve in and out without a break, so that no two facing surfaces are parallel and no wall is flat. The plan is worked out from overlapping circles and triangles, and the whole interior is white, without a single coloured marble to distract from the shape. The oval dome is the best part of the interior. It is coffered with interlocking crosses, hexagons and octagons that shrink as they climb, so the vault looks far higher than it really is, and the light comes from windows hidden at its base. Borromini finished the interior in 1641 and was still working on the street front when he died in 1667; his nephew completed it. For two hundred years guides have repeated that the whole church would fit inside one pier of St Peter's dome; the claim comes from an eighteenth-century guidebook, and it is not true.

Worth knowing

Good to know

Come in the morning — this church is closed most afternoons and much of Sunday, and a small religious community runs it, so it can also shut without warning.
Go through to the cloister and down to the crypt — both are small, both are usually open when the church is, and most visitors leave without finding either.
Follow one moulding with your eye all the way round the room — nothing in here runs straight, so tracing a single line shows you how the wall curves in and out along its whole length.
Shoot the dome from directly beneath its centre — off-centre the coffering looks like a jumble, and from the middle the pattern lines up into rings that clearly get smaller towards the top.

Things to do

1
Stand under the middle of the dome
Find the centre of the floor and look straight up: the rings of oval coffering shrink faster than distance alone would make them, which is what makes the dome look far taller than it is. The light comes from behind the cornice with no opening you can see. Then step two paces to the side and watch the illusion break.
2
Follow the curving wall with your hand
Follow the base of the wall around the interior, keeping your fingers on the moulding. It never runs straight for more than a metre or so: in, out, round a column, in again. This is a room you understand better by touch and by walking than by standing still and looking.
3
Go down to the crypt
A stair leads down to a low white crypt that repeats the curving plan of the church above at half size, with a small side chapel that has an irregular floor. Visitors rarely come down here. Borromini is said to have intended that side chapel as his own grave, and it was never used.