The fountain of the Acqua Paola was constructed for Paul V, by G.Fontana and F.Ponzio in 1612, using marble from the Nerva Forum. The water, which flows from the subterranean Aqueduct of Trajan (fed by springs near lake Bracciano, about 50 km northwest of Rome), falls into a large granite basin added by C.Fontana in 1690, beneath six columns (four of which are from the facade of Old St Peter's). From here the water is brought to Trastevere. Inside of the fountain construction now is a store of the old little fountains, parts of it and memorial tablets no longer in use.