The Acqua Felice is one of the aqueducts of Rome, completed in 1586 by Pope Sixtus V, whose birth name, which he never fully abandoned, was Felice Peretti. The first new aqueduct of early modern Rome, its source is at the springs at Pantano Borghese, off Via Casilina. Its length is fifteen miles (24 km), running underground for eight miles (13 km) from its source, first in the channel of Aqua Alexandrina, then alternating on the arches of the Aqua Claudia and the Aqua Marcia for seven miles (11 km) to its terminus at the Fontana dell'Acqua Felice on the Quirinal Hill, standing to one side of the Strada Pia (now Via del Quirinale), so as to form a piazza in this still new part of Rome. The engineer was Giovanni Fontana, brother of Sixtus' engineer-architect Domenico Fontana, who recorded that the very day the new pope entered the Lateran, he decided that he would bring water once again to the hills of Rome, which had remained waterless and sparsely inhabited, largely by monasteries, since the Roman aqueducts had been destroyed in the sixth century. From the source, which Sixtus purchased, there was only a very small fall, and the work required an underground conduit as well as an aqueduct carried on arches. The work was completed within eighteen months, at the same time that Sixtus was engaged in laying out the street plan that would provide the arteries of modern Rome.