The "Joyous Fountain" was completed in 1419 by Jacopo della Quercia to mark the arrival of running water at the heart of the city after a long aqueduct project. The marble reliefs of the Virtues and Adam and Eve are reproductions; the originals — badly weathered — are in the museum at Santa Maria della Scala across the square from the Duomo.
The fountain is fed by a 25-km network of underground tunnels (the bottini) that have supplied Siena with water since the 13th century and are still functional.