The Oratorio del Santissimo Crocifisso (Oratory of the Most Holy Crucifix) was built by Giacomo della Porta in 1568.
The oratory was built in memory of a miracle that occurred in 1519, when the nearby church of San Marcello al Corso burned down. A crucifix miraculously survived the fire while everything else was destroyed.
1522, the crucifix was carried in a solemn procession to St Peter's Basilica during an outbreak of the plague. The epidemic immediately came to an end. Four years later, in 1526, the Archconfraternity of the Most Holy Crucifix (Arciconfraternita del Santissimo Crocifisso in Urbe) was created, which was dedicated to promoting the veneration of the crucifix.
Inscription
The large inscription on the facade states that the building of the oratory was supported by cardinals Ranuccio and Alessandro Farnese, nephews of Pope Paul III (r. 1534-49).
Interior
The interior of the oratory comprises a single rectangular space without side chapels. The frescoes on the side walls and the counter-facade depict the story of the miraculous crucifix, the Legend of the True Cross and the history of the Confraternity.
Copy of the Miraculous Crucifix
The crucifix in the sanctuary is an 18th century copy; the original was returned to the church of San Marcello al Corso.