Basilica, which is part of the patrimony of Constantine Order, since 2006 also homes Constantinian Museum. The first stone of the building was laid in 1521 by Bishop Nicholas Urbani. The work was entrusted to architects Bernardino and Giovan Francesco Zaccagni from Torrechiara. The building is set on a Greek cross, with arms locked by four large symmetrical apses and four quadrangular chapels. The position of the windows is studied as a function of the interior paintings and the light spreads gradually throughout the church: the intermediate spans are slightly dim, the apse is illumined plentiful and Dome is hit by an intense light, amplified by the role of gold leaves in the arches and gilding of the rosettes. The interior is decorated by Parma school of the seventeenth century frescoes: the entire pictorial decoration was initially entrusted to Parmigianino, then the work was continued by Michelangelo Anselmi and Bernardino Gatti. Interesting are the works of craftsmanship of sacred furnishings of Sacristy, part of of Museum, and the stalls of Knights Choir.