Other than the perimeter of the building, only the vast area of the narthex remains from the ancient church, consecrated in 1107 by Pope Pasqual II. The covering over the entrance, a rampant arch on enormous oblique arches, dates between the 12th and the 13th century and has links to the French, Mozarabic, and Armenian cultures. The basilica is divided into five naves. In 1218, the façade, the only example of Romanesque architecture characterized by a cross between ashlar sandstone and clay brick arches interweaving in parallel couples with the two angular towers, already covered the entire area of the church. It is, therefore, probable that the place, while not being a bishopric see, had perhaps been designed in a rather ambitious way space-wise in order to adapt itself to Casale’s role as capital of the Monferrato seal. It was precisely the link of the Marquises Paleologi with the Latin empire of Constantinople that would have included, during the 1200’s, masters so expert as to conceive the grandiose and bold covering over the atrium, already with a portico, in front of the church. The narthex, with an extraordinary and unusual architecture in the vault similar to Armenian structures, is flanked by the matronaeum (women’s gallery) with four-lights windows and Romanesque capitals From the narthex, one goes down into five naves. The funerary Monument dedicated to Bernardino Tibaldeschi, the work of Matteo Sanmicheli, is located in the chapel to the left of the main altar. The figures of Santi and Angeli depicted in the choir area and in the apse’s cupola were done in 1860 by Costantino Sereno.
In the presbytery, one reaches the ambulatory where the remains of 12th century flooring and several sculptures dating from the 14th and 15th centuries are exhibited on the walls. The sacristy has collected and preserves major paintings: Gaudenzio Ferrari’s baptism of Christ, the altarpiece from Madonna con Bambino e Santi by Giorgio Alberini, and four canvases by Pietro Francesco Guala. Returning to the church, facing the nave on the left is the chapel of Sant’Evasio built during the second half of the 18th century on designs, partially modified, by Benedetto Alfieri; the bas-reliefs are the work of Giovanni Battista Berbero, while the vault’s fresco is by Giovanni Battista Ronchelli. At the center of the transept there is a silver-plated wood Crocifisso (Crucifix), made by several Lombard artists, which dates back to the second half of the 12th century. The imposing structure presents more than a few static problems, so much so that during the last century, the architect Antonelli, father of the Mole Antonelliana, was consulted to demolish it.
