This Romanesque stone building was constructed on the ruins of the paleo-Christian basilica of Santa Maria Maggiore, which was demolished between the 11th and the 12th century. It is a large, circular building with one-light windows, surmounted by a tambour with a conical roof. The old ground level, where the original main entrance was situated, can be seen around the Rotonda. The new entrance was opened in 1571 in place of the previous one. The main doorway still exists on the west side of the building, although the tower which stood over it has collapsed. The church contains several interesting works, including the imposing sarcophagus, carved in bas-reliefs of Bishop Berardo Maggi, who died in 1308. A flight of steps leads down to the interior of the Rotonda, where eight trapezoidal pilasters and round arches form a circle and support the majestic hemispheric cupola. On the left of the large, raised presbytery is the Capella delle Sante Croci (Chapel of the Holy Crosses), where precious reliquaries are kept behind a grate. To the right, in the space in front of the Capella del Santissimo Sacramento (Chapel of the Holiest Sacrament), two paintings by Romanino can be seen. In the transept, opposite the altar, there is an interesting work by Francesco Maffei from Vicenza (1656) which represents the procession during which the relics of the holy bishops were transported to the old cathedral of San Pietro. In the choir stalls there are paintings by Moretto, including the splendid “Our Lady of the Assumption”, wooden stalls decorated by Antonio da Soresina (1522) and an organ designed by Costantino Antegnati (1536). Two flights of steps - on both sides of the main staircase to the presbytery - lead to the Crypt of San Filastrio, who was Bishop of Brescia in the 4th century; the crypt was constructed making use of capitals and columns from the Roman, Byzantine and 8th-9th century ruins found in the crypt of the original cathedral.