The co-cathedral of Sant'Andrea, the largest church in Mantua, is a Renaissance masterpiece designed by Leon Battista Alberti. The crypt houses reliquaries containing soil infused with the alleged blood of Christ, brought by Longinus. Founded in 1046 and initially dedicated to Sant'Andrea, it became the center of the Military Order of the Blood of Jesus Christ since 1608. The current structure, completed in the 18th century, was commissioned by Ludovico II Gonzaga. The church welcomed pilgrims during the Feast of the Ascension, venerating a vial containing the blood of Christ. The dome, 80 meters high, was added in 1732 by Filippo Juvarra. The facade, inspired by a Roman triumphal arch, features a portico under the central arch, highlighted by Corinthian pilasters. A "sunshade" above the tympanum, considered unrelated to the original project, emphasizes the solemnity of the triumphal arch, illuminating the nave and creating an evocative atmosphere.