Initially financed by Cardinal Alfonso Gesualdo for the Order of Theatines, the church of Sant' Andrea della Valle was begun in 1591. The architects were Giacomo della Porta, Pier Paolo Olivieri, and Carlo Maderno, who designed the spectacular dome, the highest in Rome after St Peter's.
Dome
The lantern is thought to have been designed by Francesco Borromini (1599-1667). The eight windows are separated by pairs of ionic columns. Each pair has a human face where the capitals meet.
Lantern
The facade was added in 1665 by Carlo Rainaldi. It is crowned with the pope's coat of arms and emblazoned with the inscription: ALEXANDER · SEPT · P · M · S · ANDREAE · APOSTOLO · AN · SALVTIS · MDCLXV (Alexander the Seventh, Pontifex Maximus, to St Andrew the Apostle, the year of salvation, 1665).
Entrance
The four statues on the facade depict St Cajetan, St Andrew, St Sebastian and St Andrew Avellino. Domenico Guidi carved St Cajetan and St Andrew, while Ercole Ferrata carved St Sebastian and St Andrew Avellino.
Allegorical Statues of Hope and Strength
Each statue is surmounted by a pair of putti bearing symbols of martyrdom. The allegorical statues of Hope and Strength, above the main entrance, are the work of Antonio Fancelli. The coat of arms belonged to Cardinal Francesco Peretti.
Interior
The interior has a high barrel vault and a spacious apse.
Nave Vault
The four paintings in the vault of the nave celebrate the doctrine of the Immaculate Conception. The panels depict The Expulsion of Adam and Eve from Paradise and The Vision of Our Lady to Sister Orsola Benincasa by Virginio Monti, andThe Proclamation of the Dogma of the Immaculate Conception and The Visitation by Salvatore Nobili (1865-1919). The picture of The Expulsion of Adam and Eve is unusual in that it depicts Mary Immaculate remaining in Paradise.
The panels by the windows depict the Apostles and the Evangelists and are by Silvio Galimberti.
Funerary Monument to Pope Pius II
High up on the walls before the crossing are two funerary monuments, one to Pope Pius II (r. 1458-64), and the other to his nephew Pope Pius III, who only reigned for twenty-six days (r. 22.09. - 18.10.1503).
Interior of Dome
The fresco in the dome is the Glory of Paradise (1621-27) by Giovanni Lanfranco (1582-1647). His contemporary Domenico Zampieri (1581-1641), better known as il Domenichino (on account of his diminutive stature) added the frescoes in the pendentives and the scenes from the life of St Andrew in the vault of the apse.
Apse
The large paintings above and to either side of the high altar, including the Martyrdom of St Andrew, are the work of Mattia Preti (1613-99).
Cappella Ginnetti (aka Cappella Lancellotti)
The side chapels in the nave are identical rectangular spaces, each capped with a small dome.