Francesco Borromini, San Carlo alle Quattro Fontane, Rome

Geometry and motion in Borromini’s San Carlo

Francesco Borromini, San Carlo alle Quattro Fontane (“Carlino”), Rome. Commissioned by Cardinal Francesco Barberini in 1634 for the Holy Order of the Trinity; construction began in 1638 and the church was consecrated in 1646. 

Additional resources

Olivier Bernier, “Borromini’s Rome”, The New York Times, Dec. 22, 1991

San Carlo alle Quattro Fontane / Vault
by Matthew Brennan
on Sketchfab


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[0:00] [music]

Dr. Steven Zucker: [0:04] We’re in San Carlino, San Carlo at the Four Fountains, in Rome, this magnificent tiny church designed by the Baroque architect Borromini.

Dr. Beth Harris: [0:14] This church is so unexpected. When you walk inside, the walls move in and out, they undulate.

Dr. Zucker: [0:22] Everything is about movement in this church. Every architectural form seems to move. The rhythms created by the columns seem at such odds with the sense of stability that architecture generally tries to express.

Dr. Harris: [0:35] You have these engaged columns alternating with niches, and we see curving rectangular panels and arches. All of this draws our eye up to this amazing dome, but it’s not the kind of dome we expect. It’s not a perfect hemisphere. It’s an oval. The church itself is based on an oval, which you don’t immediately recognize when you walk in.

Dr. Zucker: [1:00] Borromini received this commission from the Trinitarian Order, an order that was dedicated to ransoming Christians that had been taken in war or by pirates.

Dr. Harris: [1:10] The Trinitarians had very little money, and most of this church is made out of very inexpensive materials. It’s made out of stucco.

Dr. Zucker: [1:18] Which is a little bit like plaster. It’s a soft cement that’s easy to carve.

Dr. Harris: [1:22] As we’re standing here, the door opens and closes. You can hear the traffic of the city of Rome right outside the door.

Dr. Zucker: [1:28] It’s a reminder of just how small a plot Borromini had to work with in designing this church. Now, for all its musicality, for all of its movement, for all of its energy, the church is actually based on a careful geometric structure.

Dr. Harris: [1:42] There are two triangles that share one side, and within each of those triangles are circles. Those circles are inscribed within an oval, and that oval is the primary shape of the floor plan and the dome above.

Dr. Zucker: [1:58] The two triangles together form a diamond. The opposite points of that diamond define the ends of the lobes. On one side, the apse. On the other side, the entrance.

Dr. Harris: [2:07] We have this feeling of movement, of a space that is difficult to understand.

Dr. Zucker: [2:13] The importance of geometry becomes apparent when we look up to this marvelous lobed entablature. Above that, we see these arches that stretch and deform as they span this complicated shape. Above that is dome.

Dr. Harris: [2:28] We see hexagons, octagons, crosses, and at the very center, another oval.

Dr. Zucker: [2:35] At the very top, we see a dove within a triangle, a symbol of the Holy Spirit, part of the three-part nature of God, which couldn’t be clearer set within that triangle.

Dr. Harris: [2:45] Of course, the order that commissioned this, the Trinitarians, focus their devotion on the Holy Trinity. The light in that lantern reads as supernatural light. When you stand in the center of the church, you don’t see those windows, but it looks as though light is pouring down to the earthly below from the spiritual, divine, miraculous source.

Dr. Zucker: [3:07] The whole church is a metaphor, the complexity in the lower section of the church reaching a clarity and perfection as we look up towards the heavens.

Dr. Harris: [3:16] Well, this idea that a divine geometry underlies what seems like a kind of chaos of the earthly, the idea of God as the divine geometer, and just before this church was built, Johannes Kepler wrote about how the universe was structured by the laws of geometry.

[3:38] And so, we get a sense of the movement, the chaos of the earthly, but underlying that, an order that is created by God.

Dr. Zucker: [3:47] One recent art historical study sees a relationship between the complex lobing of the church and the medieval use of the mandorla — that is, a kind of full-body halo — in which Christ is often represented.

Dr. Harris: [3:59] Although when we look around the church, we recognize the forms of classical architecture — attached columns, coffers with rosettes, an entablature, a dome — underlying this are important theological ideas. Let’s go outside and look at the exterior.

Dr. Zucker: [4:16] We’ve stepped outside, into the heavy traffic of Rome, looking at the outside of San Carlino. It could use a cleaning. Just like the inside, every architectural element on the exterior is in motion. Four large columns stand in front of a surface that undulates inward and then outward, and then inward again.

[4:33] So you have this concave, convex, concave undulation.

Dr. Harris: [4:37] And above that we see three concave spaces, although the central space projects outward because of the medallion held aloft by angels in the center.

Dr. Zucker: [4:48] Just look at the entablature and the cornice above it. It’s as if it’s the waves of the ocean, and the columns function almost like pivot points that allow the building to move in and out.

Dr. Harris: [4:58] We think about representing movement in sculpture with something like Bernini’s “David,” but here Borromini takes on movement in architecture.

[5:07] [music]

Cite this page as: Dr. Beth Harris and Dr. Steven Zucker, "Francesco Borromini, San Carlo alle Quattro Fontane, Rome," in Smarthistory, November 18, 2015, accessed June 14, 2024,