This fountain was originally built in 1586 under Sixtus the Fifth Peretti (1585-1590) by the architect Domenico Fontana, as reported by the epigraph placed in the arch of the door nearby. It was thoroughly rebuilt in 1733 under pope Clement the Twelfth Corsini (1730-1740). The fountain consists of a mask with bats’ tails that pours water in the hollow of a shell, from which it falls into a reinforced pond, together with the water coming from two sidetaps. All leans against a brick arch flanked by ashlar pillars. Clement the Twelfth’s coat of arms and an inscription commemorating the work are on the wall.