This church was built on the site where St Agnes is believed to have been martyred. It was commissioned by Pope Innocent X Pamphili, who wanted it to become his palace chapel. Rainaldi began the work, which was continued by Borromini who created the latter built part of the dome and the curving façade. In contrast to its sober exterior, the interior was embellished in the late 17C with stucco work, gilding and paintings.