the church of San Gregorio Magno of Gromo is already documented in an estimate of the XV century; the construction dates back to 1335, certainly was a private oratory of the family Ginami owner of the homonymous castle and Palazzo Milesi, now the seat of the municipality. On the back of the church, on a stone is imparted the dating partially ruined. It is precisely in this church in 1392 is drafted the document that will define the boundaries of the territory of Gromo. The main entrance of the Church is directed to the west, toward the piazza, with a 16th century portal in Sarnico stone.
The inside has a rectangular plan and a single nave divided into three bays by two orders of pilasters, with a barrel vaulted ceiling and a nineteenth-century decoration on both walls of little value. The presbytery is a recess narrower than the nave, accessible by one step in stone, with a wooden altar of simple invoice. In a wooden ancona in the seventeenth century, with two Corinthian columns lateral holding a broken tympanum with at the center the dove of the Holy Spirit, alpine-baroque style, there is placed the blade of the Holy conversation by Enea Salmeggia aka 'Talpino'.