Church of San Carlo alle Quattro Fontane

This small church, one of Borromini's earliest and most inventive works, stands at a crossroads marked by four corner fountains on the Quirinal Hill. Despite its modest footprint, the interior astonishes with an undulating play of concave and convex surfaces beneath an oval dome coffered in a geometric pattern that seems to float on hidden light. Completed in the mid-seventeenth century, it distilled Borromini's revolutionary approach to space and geometry. A quiet cloister of the same period adjoins it.