In its ciborium, the church houses the miraculous portrait of the Virgin - painted by Damiano Padovani (1646) - once placed on the south town gate. Its history is related to a miracle still vivid in the memory of the people, whose visible testimony may be found in the collection of ex-votos, located in the museum annexed to the church. The construction of the Sanctuary was entrusted to architect Prospero Mattioli from Reggio Emilia and the first stone was laid in the presence of Duchess Maria Vittoria, on August 20, 1693. At the beginning of 1703 - when the building was nearly completed - the portrait was moved inside the church. The Sanctuary was consecrated for worship only in 1709. The church has a large pronaos, divided into three arches, and its facade is characterized by the presence of a subdivision between lesenes and cornices. In addition, it includes four large niches housing statues dedicated to St. Francis of Assisi, St. Charles Borromeo, St. Peter and St. Paul - copies of original works dating back to the 18th century. The church has a Latin cross plan, of which the central nave is covered with a dome. In the upper part of the structures dividing up the naves, in the transept and in the presbytery, artworks by Giovanni Morini from Viadana (1786) are situated in deep niches. Four coats of arms are placed at the top of the arches: three belong to the Gonzaga family, whereas the fourth - located in correspondence to the “Altare della Croce” (Altar of the Cross) - represents the town of Guastalla: a rampant crowned lion on a blue background. The choir is placed on the entrance door and its balcony is decorated with several musical instruments.