Giovanni Fontana was primarily a hydraulic engineer and was a prominent member of the family workshop, directing its engineering works. One of his principal projects under Pope Sixtus V was the management of the Acqua Felice scheme (1587-1590) in Rome, involving the improvement of the aqueduct, which was still under construction, and the erection at the north-east corner of Piazza S Bernardo of a monumental fountain known as Mostra dell'Acqua Felice or Fontana del Mosè (in situ) that was designed by his brother Domenico (elevation and ground-plan in Della transportatione dell'obelisco vaticano (1590), fol. 56r). The word "mostra" (showpiece) is used to denote the terminal fountain that is a public memorial to the whole achievement of the aqueduct.