San Giacomo Gate is one of the four Venetian gates in Bergamo's old town. It was built in the late 16th century, this gate is all fancy with its white marble facade and a winged lion of Saint Mark on top. The whole Venetian Walls are a UNESCO World Heritage Site, the only one in Bergamo.
If you are coming from the station and didn't take the funicular to reach Bergamo Alta (the ancient part of Bergamo), you'll enter the historic centre from this gate. I think it's the best introduction to the ancient city and you get to see right away the Venetian walls.