Built before the Bell tower, the Church of St. Mary in Trivio in Velletri was originally in the Gothic style, with a bare planked ceiling. It was falling into disrepair by the first half of the 17th century so the architect Carlo Maderno was commissioned by Bishop Cardinal Raniero D'Elci in 1759, to design a new church, on a Latin cross floor plan with central cupola, side chapels and a sumptuous façade.
During WWII, air and naval bombing raids demolished a large part of the central nave and the apse.
Civil engineering moored the static part of the church and the Tabernacle was recreated in marble and mosaic, although some reconstruction work still needs to be carried out.
There are some paintings and canvases of value in the church. The large canvas of the Assumption of the Virgin on the main altar was painted by Giovanni Sorbi of Siena in the early 18th century while the painting of the Virgin and the Saints in the Chapel of St. Anthony, first on the left, is by Sebastiano Conca.
The Bell tower of St. Mary in Trivio is one of the most famous in Italy because of its height and its excellent condition. The name Trivio refers to the junction of three streets that occurs just outside the church, although the bell tower is generally referred to as the Bell tower of St. Mary because it was built for the previous church of Our Lady Assumed into Heaven.
The tower was built by the famous Comacine Masters, known as the 'Magistri' of the building art, during the first phase of the renewal of Italian art. Today, it stands over 40m high. It was originally not detached from the church, the separation only took place in 1622. It was also badly damaged by bombing in WWII, but was carefully restored by the Superintendent of Historical Monuments.