Like many buildings of the Catholics religion, even the cathedral was built on a pagan temple. We are at the highest point of Frosinone and here stood the acropolis of ancient Frusino with the temple dedicated to the god Mars. Already in the eighth century, the church was the cathedral of an ancient diocese of Frosinone that then joined the Diocese of Veroli.
The church was later rebuilt in the Middle Ages assuming a Romanesque style of which traces remain in the 68 meters high bell tower. The bell tower has three rows of mullioned windows surmounted by an octagonal dome and is considered the ‘symbol’ of the city.
The cathedral took on its present appearance in the eighteenth century with a late Baroque shape reminiscent of Sant’Andrea della Valle in Rome
The interior of the church has three naves separated by Corinthian pilasters and the church had to be partially rebuilt after the bombings of World War II.
Inside are the canvases painted in 1641 by Sermenti, a disciple of Guido Reni, depicting the Madonna with Saint Anne and Saint John with the angels. The church contains other works by contemporary artists.
At the sides there are the bronze statues of the two popes of Frosinone Saints Hormisdas and Silverio, patrons of the city.