This Church, first called S. Pietro, is mentioned in documents from 1116. In the second half of the 12th century it is documented as S. Pietro a Ischia (ad insula) and in the late 13th century is under the patronage of the Galletti family, who restructured it in 1277.

In 1393 an altar, dedicated to St. Francis was built, carved by Francesco di Cristiano. In the early 17th century, when a relic of St. Apollonia was discovered beneath the main altar, the Church took the saint’s name. In 1777, when the male line of the Galletti family died out, patronage of the Church passed to the wife and daughters who charged Mattia Tarocchi with redesigning the interior and exterior of the Church in its present Baroque style, as a plaque on the left of the door commemorates. The church at present not used for worship; it is the UNITALSI headquarters.

The front is particularly interesting. It is slightly concave and flanked by double pilasters, with a centrally placed oval window, surmounted by a pediment of opposed semicircular scrolls.
The hall-shaped interior is covered by barrel vaulting. Large tempera paintings by Giuseppe Bocchini (1820) adorn the walls. The main altar in marbled stucco is late 18th century. Behind it is a semicircular apse decorated with a trompe l’œil fresco, the work of Mattia Tarocchi, depicting a canopy with St. Peter at the centre; below at the sides aretwo allegorical figures by Giovanni Battista Tempesti.