It is the most characteristic squares of the city; the neighborhood where it is located in the narrow streets and dark alleys, palaces closed testify to a past world and a glorious tradition and full of charm. The history of the square dates back to ancient Rome. On the whole area rose the vast circus of Emperor Domiziano, on the steps of which are now built the houses that surround the square today. Here were held mock naval battles, magnificent public shows, games, ect. Later, although the complex was left in ruins until it disappears, at the people continued to enjoy themselves. In the Middle Age holidays popularity continues to unfold here. Even in the nineteenth century the wandering comedians with their antics, fun people here on sundays and feast days in the month of August, spent time splashing around in the water without overflowing fountains, to the great amusement of the cardinals and the rich, who threw money out of their cars by the handful to increase the gaiety of the people.

Today is the big Christmas market, which brings to life all the past of the square. The current form of the rectangular square, with its fountains, the church of San Agnese, the Palace Pamphili and the buildings that surround it, was built between 1600 and 1700. Since then almost nothing has been changed and this is the secret that characterizes it. Pope Innocenzo X began to arrange the square, until then dirty and neglected, with the reconstruction of the Palace Pamphili, who ordered to Girolamo Rainaldi. The grand palace with its simple mass gave immediately to the whole environment a distinct character to which were added after the other buildings.

The interior is remarkable for the decoration of the hall with frescoes by Pietro da Cortona, famous artist from Florence. The Pope had also raise the church of San Agnese, the place where the saint was martyred. Already in the Middle Age it was here erected a church on the walls of the circus. The remains of this can be seen at church today. The church is the work of Borromini (1645-50). The artist was particularly criticized and mocked for the swaying of the Baroque facade, for the lightness of the towers and the dome, and the new conception of the whole. The most ruthless critics was his eternal rival Bernini.

The artist, suffering and weak, was so distressed by the incessant criticism that ended with suicide. The interior of the church is by Carlo Rainaldi, richly decorated in accordance with the baroque spirit. Pope Innocenzo X was buried here. Once the square, the Pope continued to embellish it with the construction of two fountains. One of these, Bernini's masterpiece, is the central fountain of the rivers. On the group of rocks sit the giants symbolizing the rivers of the four continents: the Nilo, the Gange, the Danubio and the Rio of Plata. Above rises the obelisk of Domiziano. The other, in front of the palace Pamphili, is the fountain of Moro.

The third fountain, to the other side of the square is a recent work of the nineteenth century. Today the square is surrounded by characteristic coffees and wine bar in the center of the square painters exhibit their works, and the Romans, adults and kids are walking by creating an indissoluble harmony between art, history and real life.