Piazza del Popolo is a large urban square in Rome. The name in modern Italian literally means "People's Square", but historically it derives from the poplars (populus in Latin, pioppo in Italian) after which the church of Santa Maria del Popolo, in the northeast corner of the piazza, takes its name.
The piazza lies inside the northern gate in the Aurelian Walls, once the Porta Flaminia of ancient Rome, and now called the Porta del Popolo. This was the starting point of the Via Flaminia, the road to Ariminum (modern-day Rimini) and the most important route to the north. At the same time, before the age of railroads, it was the traveller's first view of Rome upon arrival. For centuries, the Piazza del Popolo was a place for public executions, the last of which took place in 1826.
The layout of the piazza today was designed in neoclassical style between 1811 and 1822 by the architect Giuseppe Valadier, He removed a modest fountain by Giacomo Della Porta, erected in 1572, and demolished some insignificant buildings and haphazard high screening walls to form two semicircles, reminiscent of Bernini's plan for St. Peter's Square, replacing the original cramped trapezoidal square centred on the Via Flaminia.
Valadier's Piazza del Popolo, however, incorporated the verdure of trees as an essential element; he conceived his space in a third dimension, expressed in the building of the viale that leads up to the balustraded overlook from the Pincio (above, right).
The aqueduct carrying the Acqua Vergine Nuovo was completed in the 1820s, and its water provided the opportunity for fountains and their basins that offered the usual public water supply for the rioneor urban district. Ever since the Renaissance such terminal fountains also provided an occasion for the grand terminal water show called in Rome a mostra or a show. "What makes a fountain a mostra is not essentially its size or splendor, but its specific designation as the fountain that is a public memorial to the whole achievement of the aqueduct." Valadier had planned fountains in the upper tier of the Pincio slope, but these were not carried out, in part for lack of water.
Fountains by Giovanni Ceccarini (1822–23), with matching compositions of a central figure flanked by two attendant figures, stand on each side of the piazza to the east and west, flanked by neoclassical statues of The Seasons (1828). The Fontana del Nettuno (Fountain of Neptune) stands on the west side, Neptune with his trident is accompanied by two dolphins. Rome between the Tiber and the Aniene on the east side, against the steep slope of the Pincio, represents the terminal mostra of the aqueduct. Dea Roma armed with lance and helmet, and in front is the she-wolf feeding Romulus and Remus. At the center of the piazza is the Fontana dell' Obelisco: a group of four mini fountains, each comprising a lion on a stepped plinth, surround the obelisk.