Monte Lesima is the fourth highest peak of the Ligurian Apennines for altitude, with its 1724 m it separates the Scrivia Valley from the Trebbia Valley.
At the top stands a large metal lattice cross. It was blessed on November 5, 1954 by the bishop of Bobbio during a historic mass that attracted the faithful in procession from Zerba, Pej, Corbesassi, Bogli and all the surrounding villages on a beautiful sunny day.
In the late 1980s, a massive geoid-shaped radar was built near the cross. It is used by ENAV for air traffic control at numerous Italian airports, in Zurich and Marseille. The white globe has become an unmistakable symbol of Lesima, clearly visible even from far away. The structure is reached by an asphalted roadway that climbs along the grassy north-west ridge. Until 2008 it was manned 24 hours a day by specialized personnel, while today it is only remotely monitored as it has been made completely automated.