Santissima Trinità, Romanesque church in Casnigo, Italy.

Santissima Trinità is a church in Casnigo standing at about 700 m on a hill below Monte Farno, near Ronco Trinità. It grew in at least three stages: an early chapel absorbed into the entrance porch, a 15th-century hall with frescoes, and a taller 16th-century hall built between 1575 and 1596. A bell tower with an onion dome rises at the end of the 16th-century enlargement.

A medieval watchtower originally stood at this site and controlled large portions of the Seriana Valley before the church construction began in several phases. This transformation from military to religious purpose shaped the development of this location.

The church displays two major fresco cycles created by the Marinoni and Baschenis families, whose works decorate the interior walls with religious scenes. These paintings reflect the artistic tastes of the local community during the Renaissance.

The site sits on a hillside with good accessibility from surrounding walking trails. It is wise to wear sturdy footwear since the paths are sometimes steep and surfaces are uneven.

The oldest section keeps its original terracotta floor, whose date the sources do not fix. The bell tower, added in the sanctuary's last enlargement at the end of the 16th century, is topped by an onion-shaped dome. Inside, a locally carved stone block holds an old metal alms box with a double lock.