The Parish Church of San Martino, built in 1666 on the remains of a pre-existing building dedicated to worship, within the castle, is worth visiting.

In 1835, it was decorated and expanded by the architect Gagliardi from Mortara, transforming it into a three-nave church. However, the most beautiful image is that of the Blessed Virgin of Donzellina, named after the location near Tromello where the fresco was originally placed, believed to have miraculous powers.

It was later moved to safety in the sacred place and is still venerated by the local faithful. Notably, the area surrounding the church is part of the ancient medieval defensive settlement. In 1962, a new baptistery was also built.

In Tromello, there is also an ossuary decorated with painted stucco, a reminder of ancient cemeteries and plagues. To commemorate the deliverance from these calamities, the church of the Confraternity of San Rocco was erected at the end of the 1500s, restored in the early 1900s. It is in Baroque style, and perhaps not everyone knows that it has a rooster-shaped weather vane at the top of its bell tower, indicating the direction of the winds.