Fontana delle Tartarughe first water flowing to a reservoir near the present Trevi Fountain. Della Porta and the city of Rome made a plan to build eighteen new fountains connected to the new aqueduct. He began in 1572 with the fountain in Piazza del Popolo, then built the two famous fountains of Piazza Navona (1574–1578), and the fountain in Piazza della Rotonda in front of the Pantheon (1575). + In the original plan of 1570 a new fountain was to have been placed near the Theater of Marcellus in the Piazza Giudea, the site of a market in the Roman Ghetto. One of
Sant'Agnese in Agone plan but made adjustments; on the interior for instance, he positioned columns towards the edges of the dome piers which had the effect of creating a broad base to the dome pendentives instead of the pointed base which was the usual Roman solution. His drawings show that on the façade to Piazza Navona, he designed curved steps descending to the piazza, the convex curvature of which play against the concave curvature of the façade to form an oval landing in front of the main entrance. His façade was to have eight columns and a broken pediment over the entrance. He