Of ancient foundation, the church of Sant' Agnese in Agone stands on the site of the Stadium of Domitian, the traditional site of the martyrdom of St Agnes.
St Agnes is one of the great Roman virgin martyrs. Before her execution in 304 she is said to have been exposed in a brothel, where a young man who looked at her naked was struck blind. Her hair then grew miraculously to hide her nakedness. This event allegedly took place in one of the arch-vaulted chambers under the terraces of the Stadium of Domitian, and her execution then occurred in the stadium itself.
The church was rebuilt by Girolamo Rainaldi and his son Carlo, at the behest of Pope Innocent X (r. 1644-55), whose family palace stood next door. In 1653 the pair were replaced by Francesco Borromini, who added the splendid concave facade.
Dome
He, too, was soon replaced and the work was completed by Giovanni Maria Baratta, who added the twin bell towers. The facade sports a single statue, that of St Agnes.
The octagonal dome sits on a high drum with a large rectangular window on each of its eight sides.
Lantern
The lantern is Carlo Rainaldi's design. The windows are surmounted by the heraldic devices of the Pamphilj family, namely fleur-de-lys and a dove with a sprig of an olive tree in its beak.
Interior
The layout of the interior is based on a Greek cross plan.
Interior of the Dome
The fresco in the cupola depicts The Apotheosis of St Agnes and is mostly the work of the Roman painter Ciro Ferri (1634-89), a pupil of Pietro da Cortona. However, Ferri died before finishing the fresco and this task fell to his pupil Sebastiano Corbellini. The pendentives were painted by Giovanni Battista Gaulli (1639-1709), better known as il Baciccio or il Baciccia, and depict allegories of the four Cardinal Virtues. The inscription at the base of the dome reads: INGRESSA AGNES TVRPITVDINIS LOCVM ANGELVM DOMINI PREAPARATVM INVENIT(On entering the place of shame, Agnes found the angel of the Lord ready).
High Altar
The seven altarpieces all take the form of bas-reliefs or statues rather than paintings. The high altar sports a bas-relief of The Holy Family with St John the Baptist and his Parents (1683) by Domenico Guidi. The altar is surmounted by three putti holding a bronze scroll, which reads: NON SVRREXIT INTER NATOS MVLIERVM MAIOR IOANNE BAPTISTA(None has arisen among the sons of women greater than John the Baptist), a possible reference to the pope who was born Giovanni Battista Pamphilj.
Statue of St Agnes by Ercole Ferrata
The Chapel of St Agnes occupies the right arm of the Greek cross. The statue of St Agnes Among the Flames is by Ercole Ferrata (1610-86). The flames represent the fires of sexual temptation. Above the vault are a pair of angels carrying the symbols of martyrdom (palm branch and crown), also the work of Ferrata. Above these he executed three putti holding a text proclaiming: IN MEDIO IGNIS NON SVM AESTVATA (In the middle of the fire I am not burned).
The Chapel of St Sebastian occupies the left arm. The statue of St Sebastian (c. 1703) is by Pier Paolo Campi (1668-1764).
The four small chapels, which are sited in the piers supporting the dome, are dedicated to St Cecilia (top left), St Emerentiana (top right), St Alexis (bottom right) and St Eustace (bottom left).
Sacra Testa of St Agnes
A small chapel at the back of the church houses the putative skull of St Agnes.
Funerary Monument to Pope Innocent X
High above the main entrance is the funerary monument (1730) to Pope Innocent X, the work of the sculptor Giovanni Battista Maini (1690-1752).