This church, frequently used for state ceremonies, was founded in the mid-16th century inside the Diocletian Baths. It was built to designs by Michelangelo, who sought to minimise alterations to the original building, simply linking several different spaces and conserving the original walls and columns. A less respectful reconstruction was carried out, in honor of the holy year 1750 by Vanvitelli, who altered the angle of its positioning. Salvator Rosa and Armando Diaz are buried here. Amongst the works of art is a painting by Domenichino, to be found in the presbytery, The Martyrdom of Saint Sebastian. In the sacristy, Michelangelo's original designs are on show.