Exterior view

The church was intended to be a family chapel annexed to the adjacent Palazzo Pamphilj. The first designs were made by Girolamo Rainaldi and his son Carlo Rainaldi. In 1653, the Rainaldis were replaced by Francesco Borromini, but in 1657 Borromini resigned and Carlo Rainaldi was reappointed. In 1666 Gian Lorenzo Bernini took over the construction and the edifice was completed in 1672.

The centralized interior of Sant'Agnese has a Greek-cross plan with short, barrel-vaulted arms, and beveled piers at the crossing, into which niches are let. The niches are flanked by matched Composite order pilasters and columns of veined marble. Rainaldi intended the columns to be recessed, but Borromini changed the profile of the beveled piers to make them seem free-standing. The altars in the niches serve as bases for huge scenes of martyrdom carved in marble relief. The dome fresco was begun by Ciro Ferri in 1670.

View the ground plan of Sant'Agnese in Agone, Rome.