The fountain of the Acqua Marcia, renamed Aqua Pia in honour of Pious the Ninth Mastai Ferretti (1846-1878), who restored it was once placed in a different position from the current one, approximately where the small obelisk of the monument to the soldiers fallen at Dogali is placed today. 

A new fountain designed by Alessandro Guerrieri was placed at the centre of the large exedra of the Thermae of Diocletian in 1888 during the works for the restoration of the area of Termini. The circular pond was firstly decorated with four temporary (plaster) lions and then in 1901 with the bronze Naiads by the sculptor Mario Rutelli. The shapely female figures caused violent disputes by many that considered them to be too provocative. The central group was added only in 1911. 

The first version, a marble group also by Mario Rutelli was not appreciated at all by the Romans that immediately called it irreverently “fritto misto” (mixed fry), so it was soon removed and “confined” in the gardens of Piazza Vittorio where it is currently situated. 

When in 1913 the imposing group of Glaucus was placed at its centre, this fountain that is unanimously considered to be the most beautiful fountain in Art Nouveau style of the time of Umberto the First, finally assumed its current appear ance.