Considered by some scholars to be the first Forlì cathedral, it stands in piazzetta Melozzo degli Ambrogi on the foundations of an older sacred building.
The original orientation of the building was the opposite of the current one, so the entrance was facing the external part of the city, serving as an invitation to pilgrims coming from outside. The current disposition was completed in 1782. The only one part of the ancient building is the 14th century bell tower.
Until the Baroque rearrangement at the end of the 18th century, the church was a place for the tombs of great Renaissance artists from Forlì, including the tomb of Melozzo degli Ambrogi, a painter loved by Caterina Sforza.
To the left of the entrance there is an episcopal chair made of veined Greek marble, dating back to the 5th century AD which is believed to have been the chair of San Mercuriale, the first bishop of the city.
On the altar of the fourth chapel on the left, hidden by an altarpiece by the painter Giacomo Zampa from Forlì, there was found a part of a fresco dating back to the 15th century. This is what remains of a triptych (the central altarpiece and the right one) depicting Christ at the column and Saints, the work of an unknown author.
Not far from the Trinity Church, you can find the remains of the Morattini Bridge, protected by a glass plate, that are visible at street level. Composed of a single round arch, built in brick with marble inserts, the oldest bridge in the city was isolated from the other ones that arose in the early Middle Ages as it was placed on the canalized city branch of the Montone river.
On the evening of 27 August 1495, the Morattini Bridge was the scene of the deadly ambush of Giacomo Feo, second husband of Caterina Sforza.