Piazza Navona

The square keeps the shape of the building it replaced. The Stadium of Domitian was raised under that emperor in the 80s AD, a running track rather than a chariot circuit: it had none of the carceres or the central spina of the Circus Maximus, only open ground for athletes, and it was restored in the third century by Alexander Severus. It measured 265 metres by 106 and could hold 30,000 spectators, who came to watch the agones, the games, from which the place took the name in Agone.

The stadium was richly furnished with statues, among them the figure known as Pasquino, thought to be a copy of a Hellenistic Pergamene group and now standing in the small square beside Piazza Navona. After the fall of the Western Roman Empire the building fell into ruin and was quarried for its stone, and little of it survives. The obelisk at the centre of the square never belonged to it, having been brought in pieces from the Circus of Maxentius on the Appian Way.

Between the tenth and eleventh centuries the Campus Agonis and its cryptae belonged entirely to the Abbey of Farfa. In the thirteenth century the ground passed under the Roman magistrate of the Capitoline chamber, which set it aside periodically for games, and ownership was for a time divided between private holders and church bodies. The use stuck: well into the Renaissance the space still served for knightly training and carnival games, with carnival held here in the second half of the fifteenth century under Paul II and a joust staged on St Mark's day in 1476 by the family of Sixtus IV.

In 1477 Sixtus IV ordered most of the market on the Campidoglio moved to the square, which fixed it as public space. The stalls were set out along the oval, which gave the market its character, and trading stopped in the hot months, when the square was deliberately flooded to cool the population.

The square was rebuilt as a display of the Pamphili family, in something like competition with the Barberini and the Farnese, during the pontificate of Innocent X, born Giovanni Battista Pamphili, who reigned from 1644 to 1655 and whose family palace faced it. Palazzo Pamphili went up between 1644 and about 1650 to designs by Girolamo Rainaldi, with the long gallery designed by Borromini and frescoed by Pietro da Cortona; whole blocks were demolished to clear the ground, among them the Cybo and Mellini palaces. The contest for the commissions was fought between the leading architects of the day with no expedient ruled out, and Donna Olimpia Maidalchini, the pope's influential sister-in-law, had a hand in choosing the artists. It was said that Bernini gave her a silver model of his design for the fountain; by other accounts it was she who chose Borromini to replace Rainaldi in finishing the church.

Bernini's Fountain of the Four Rivers, carrying the Danube, the Ganges, the Nile and the Río de la Plata as the four corners of the earth, was made between 1648 and 1651 and carries the obelisk above it. The church of Sant'Agnese in Agone, begun in 1652 by Girolamo Rainaldi and taken over by Borromini in 1653, with Carlo Rainaldi and others also at work on it, marks the spot where Agnes is said to have been martyred, and stands where a small parish church had existed since the Middle Ages. At the southern end, the Fontana del Moro had been given its basin and four Tritons by Giacomo della Porta in 1575, and Bernini added the Moor wrestling a dolphin in 1673. The old story that Bernini's Nile veils its head to avoid the sight of Borromini's facade, and that the Río de la Plata throws up a hand against its collapse, does not hold: the fountain was finished before the church was begun, and the Nile is veiled because the river's sources had not then been found.

From 1652 the square was flooded every Saturday and Sunday in August in elaborate celebrations of the Pamphili family. The pavement had earlier been concave, and the outlets of the three fountains were stopped so that the water ran out across it. In a sonnet the poet Belli evoked a harder side of the same square in papal Rome, where a public pillory stood and the sentence generally left the torturer free to increase a corporal punishment as he saw fit, for the benefit of the watching crowd. Mounted horse races were run here between 1810 and 1839. Pius IX abolished the water games for good in 1866 on grounds of hygiene, the pavement level was raised during the same century, and in 1869 the market went to nearby Campo de' Fiori.

The northern fountain, originally the fontana dei Calderari and dating from 1574, is the work of Gregorio Zappalà and Antonio Della Bitta; Della Bitta's statue of Neptune was added in 1878 to balance the Fontana del Moro. What remains of the market is seasonal, running from the first week of December to the first week of January and keeping its traditional weight at Epiphany with the Befana of Piazza Navona. Since the war painters and portraitists have set up easels here to work and to sell, and street performers have joined them. On 3 September 2011 a man climbed into the Fontana del Moro with a large rock and decapitated several of the figures; the police identified him from security-camera footage by his shoes.