The building was designed and erected by Filippo Juvarra after the collapse, in 1714, of the domed structure in an advanced stage of construction, commenced in 1675 and designed by the Lugano-born architect Antonio Bettino.
After producing many designs, Juvarra eventually plumped for a large
single aisle covered by a barrel vault with large windows. The
continuous polychrome trabeation and the curviliniear link at the
corners of the vault helped conjure up the perception of a unitary
Externally, the vault is buttressed by robust brick separators. The
entrance is on the same axis as the atrium of the palazzo Asinari di San
Marzano and is withdrawn from the street to allow access to the
Oratory. Juvarra's designs for church and convent were completed by
Giovanni Battista Sacchetti and Giovanni Pietro Baroni di Tavigliano,
Pietro Bonvinci (presbytery and sacristy), Giuseppe Talucchi (from 1825)
and Ernesto Camusso (facade with Corinthian pronaus, 1891).