San Carlo Alle Quattro Fontane, dedicated to Saint Charles Borromeo, was constructed in the mid 17th century after the erection of the cloister and monastic buildings. While the design of the structure was conceived and approved in the 1630s, production did not begin until nearly ten years later, and completion wasn't achieved until after Francesco Borromini, the architect, passed away. The location of the church is settled at the southwest position of the intersection of two roads, Strada Pia and Strada Felice, known as the Quattro Fontane, where four fountains grace the corners of the junction. Using a difficult site and unique aspects, Borromini designed San Carlo Alle Quattro Fontane with extraordinary qualities that constitute an nontraditional structure that soothingly fits the cramped space of the location, with an end result that is both complex and breathtaking. Hiding the unusual elongated shape of the interior, the two-level edifice of the church features a plethora of columns, windows, niches, and sculptures of angels and saints, creating an interesting mix of classic and unconventional design elements in the original structure of the church and cloister, sometimes referred to as the hidden gem of this church. Geometric themes, mainly elongated octagons on an oval base, are repeated throughout the entire structure of the church, cloister, crypt, and gardens, broken up and unified with columns and design details, such as domes and arches. Altogether, the ultimate intention of the composition is to enhance the soul's experience, to uplift the mind and spirit through the use of light and structure.