The Saint Ambrogio Parish Church rises on the highest and most scenic spot of the village (310 m or 940 ft. above sea level). Since May 2005, a very powerful binocular is permanently positioned on the square facing this Church.

This place has always been called "the Castle", because there, a fortified building rose during the Middle Ages.
The symbol of the village is the stand out Baroque church of Saint Ambrogio; it's a place with an extraordinary panoramic view. The church was built between 1772 and 1783 on the foundations of a XVII century complex, consisting of a strengthened building, a cemetery, the walls and a 15th-century chapel.    
The engineer that built it was Evasio Andrea De Giovanni from Casale Monferrato, a collaborator of the famous architect Magnocavallo.    
The inside, with its aisle in oval form, is ample and shows sober and elegant lines.   
Valuable is the high altar in polychrome marbles. Noteworthy is the painting called, "The Marriage of Saint Catherine of Siena," a work by Sister Orsola Caccia (daughter of "Il Moncalvo") which came from the ancient, and now disappeared, trevillese church devoted to Saint Catherine.