Converted into a church by Gregory III in 741 over the martyrdom place of the saint (hence its name), it was restored by Orazio Torriani in 1610 for the Benedictine monks of Montecassino. 

The facade has two late-renaissance orders. In the lower order is a portal with a triangular gable sided by two niches; in the centre of the upper order is an infilled window crowned by a triangular gable. 

The interior has a rectangular nave with two side chapels. In the chapel to the right are two angels supporting Pier Leone Grezzi’s painting ascribed to Gian Lorenzo Bernini. In the chapel to the left is a grille through which it is possibile to see the garden with the well where St Callixtus had been martyrized. On the main altar is a work by Avanzino Nucci: St Callixtus and other saints worship the Vergin.