From Colle Aperto in Città Alta, a small funicular climbs the outside of the Venetian city walls to the hilltop village of San Vigilio. The ride takes only a couple of minutes, but the view that opens up at the top -- across the rooftops of the Upper Town, down to the plain of Lombardy -- is one of the best in Bergamo.
At the top you will find the ruins of a small castle, a church, and a handful of restaurants with terrace seating. In summer one of the bars sets up outside tables overlooking the town, which makes for a memorable spot to have a drink as the light fades. The quiet lanes around San Vigilio are good for a short walk before riding back down.
The funicular entrance is just past the Porta Sant'Alessandro gate, on the right.