Located in Piazza Sant’Ambrogio, the church is one of the most important monuments of paleochristian and medieval art of Milan. The building was erected around 384 on the will of the Bishop of Milan Ambrose to preserve the remains of the Saints Gervaso and Protaso, the first martyrs died during the imperial persecutions.
Nowadays the remains are preserved in the crypt. In a letter to his sister Marcellina, Ambrose writes his will to be buried under the Altar of the church, which was named at his death after him: Basilica di Sant’Ambrogio. The church has got two bell towers, the monks’ tower on the right and the priests’ tower on the left side.
The portico of Ansperto, a cloister that precedes the entrance to the church, was once used to shelter and host the pilgrims or as a place for the market. Of great importance is the presbytery with its peculiar ascent from the crypt to the tiburium, with the golden altar and the Ciborium, where in the tenth century the scene representing Ambrose, Saints Gervaso and Protaso while receiving the Ciborium as a gift from the monks (customers).