I don't know how long you're staying in Bergamo, but If I were you I wouldn't miss a visit to the Serio river waterfalls. The river had been diverted by a dam in the 1930s and the falls disappeared. Nonetheless, five times a year the dam gates are opened to restore the original water flow, for tourists and visitors to enjoy.
Here is the calendar (italian only, alas) :
http://www.turismovalbondione.it/news_eventi.php?categoria=cascate
From Bergamo it's an hour drive north to the tiny town of Valbondione. It's the valley's end, so you can't miss it! Leave the car over there (temporary parking lots are set up, to accomodate visitors' cars) and walk uphill for a couple of hours till you reach a large meadow where you can enjoy the scene. The show starts at 11AM, when the people at the dam play a loud horn, to warn people downstream about the arrival of the water. After some five minutes, you see the water flowing down !