The Fontana del Nettuno (Fountain of Neptune) is a fountain in Rome, Italy, located at the north end of the Piazza Navona. It was once called Fontana dei Calderari because it was located close to a small alley with blacksmith's workshops, makers of pots and pans and of other metal based businesses, all of them generating heat.
The restoration of the Roman Aqua Virgo aqueduct in 1570 was immediately followed by the start of work on a continuation water supply pipe towards the district of the old Campo Marzio, which following the diminution of the city's size and importance was left as the most densely populated part of the city. Restoration of a piped water supply in turn permitted the construction of several public fountains. The basin part of the Fontana del Nettuno, (without the sculptures) was designed in 1574 by Giacomo Della Porta, who also designed the Moor Fountain at the other side of the square. It was sponsored by pope Gregory XIII. The lower part of the basin consists of white marble and the upper part of the local stone from Pietrasanta.