The Church of San Carlo alle Quattro Fontane also called Church of San Carlino (little Charles) because of its small size. The building is the first extravagant work of Borromini erected in 1640. There is a particularly pretty work of art the Saint Trinity by Mignard on the high altar a small 18th Century cloister with two orders of columns. It also has a peculiar triangular bell tower inside which the plan and the lacunar dome can be seen.
