Santa Maria dei Miracoli is one of the 'twin' 17th century churches on the Piazza del Popolo, the other being Santa Maria in Montesanto.
In 1662, Pope Alexander VII (r. 1655-67) ordered a pair of churches to be erected on the south side of Piazza del Popolo to provide a grand backdrop to the square from the viewpoint of anyone entering through the Porta del Popolo.
Cardinal Girolamo Gastaldi put up a large sum of money in exchange for being commemorated in the decoration of the two churches. The first architect was Carlo Rainaldi, who planned two identical buildings. Unfortunately, Pope Alexander died in 1667 and his successors had little interest in the project. Work stopped for four years but resumed in 1671 under Carlo Fontana. Santa Maria in Montesanto was finished in 1673 in time for the Jubilee of 1675. Santa Maria dei Miracoli was completed three years later.
At first glance the two churches seem to be identical in design, but this is not the case. For instance, the dome of Santa Maria dei Miracoli is octagonal, while that of Santa Maria in Montesanto is dodecagonal. The lanterns are also subtly different, as are the bell towers.
The design of the bell tower is attributed to Girolamo Theodoli.
The facade is dominated by the portico, which bears a dedication to Cardinal Girolamo Gastaldi. The ten statues on the roof line depict various saints. Eight of are Franciscans, recalling the Tertiaries, who used to run the church.
The church has a circular ground plan with four chapels.
Above the entrance to the sanctuary, which houses a copy of the miracle-working icon after which the church is named, is the coat-of-arms of Cardinal Gastaldi. The side walls have matching funerary monuments to Cardinal Girolamo Gastaldi (left) and Cavalier Benedetto Gastaldi. Each monument has two seated allegorical Virtues: Faith and Hope (left) and Prudence and Temperance. The bronze busts are by Girolamo Lucenti, while the statues are by Antonio Raggi.