The work transformed the small sixteenth century oratory with its simple rectangular interior, into the church we see today which has good reason to be considered the architect’s masterpiece for its balance and proportion.

Based on a Latin cross floor plan, it is surmounted by a barrel vault roof and a cupola placed in the intersection with the transept. The spandrel is decorated by frescoes depicting the Four Evangelists by Francesco Podesti, dating to 1880. The stucco statues of the apostles along the walls and the Gloria above the high altar piece entitled The Institution of the Eucharist by Francesco Caccianiga, are by Gioacchino Varlè (c.1775). In the apse, which is laid out on a quadrangular floor plan, Ciaraffoni achieves a semicircular depth by means of a highly effective use of perspective.

On the outside, the church was flanked by two higher palazzi which contributed to highlight the cupola and winding bell-tower of Borrominian influence. The palazzo nearer to piazza della Repubblica was hit by the bombings of 1943 and was never rebuilt, highlighting the lack of facade overlooking the square and breaking the harmony of the whole complex.