The village of Pessano which like Paerno, contributed to populating the hamlet of Bollengo, in 1250, quickly disappeared, while the Romanesque church of the hamlet protected by the Cathedral Chapter of Ivrea, has been preserved to this day.
The bell tower is located centrally to the façade, being a clocher porche (bell tower porch); from here the single apsed nave is accessed, divided into two bays by a wide arc; on the walls there are the remains of frescoes dating back to the fifteenth century and an ancient section of lattice work with a geometric crosshatch design. On the right side of the building there are two more recently added presbytery rooms. The bell tower is spread over six floors and has five background paintings surrounded by pilasters and suspended arches; the slit openings on the third floor are located in the upper part a single light window and two mullioned windows with two lights.