Ideas for Bergamo

Take the funicolare up to the Citta Alta and wander around. The Colleoni chapel is magnificent. There's also a citadel with a WW2 memorial that is a good vantage point for taking photos of the upper city. There are several good restaurants to have lunch up there - but if you want something cheap and quick I highly recommend Polentone https://goo.gl/maps/U1YWrMV1dfPkCneM6

The polenta taragna with cinghiale ragu was amazing

Bergamo is great. Spend ALL of the available sightseeing time up in old Città Alta - upper Bergamo - that's perched above the modern city. It's compact and easily walked, and just strolling about taking in the architecture can be enough! Some ideas here:

https://www.visitbergamo.net/en/upper-bergamo/

As well, check out the basilica, Colleoni Chapel, and baptistry:
https://www.visitbergamo.net/en/object-details/23-santa-maria-maggiore-basilica/
https://www.visitbergamo.net/en/object-details/25-battistero-(baptistery)/
https://www.visitbergamo.net/en/object-details/18-colleoni-chapel/

Walk the Venetian Walls and take in the expansive views:
https://www.visitbergamo.net/en/object-details/2979-venetian-walls-and-unesco/

Take the S. Vigilio funicular even higher for even lofter views, the ruin of San Vigilio Castle and pleasant walkabout:
https://www.visitbergamo.net/en/object-details/3369-s--vigilio-funicular/
https://www.visitbergamo.net/en/object-details/20-s--vigilio-castle/

We had a fun (and very good) dinner here: if at all possible, eat outside under the greenery-festooned canopies:
https://www.ilcircolinocittaalta.it/en/

Use a translation tool for the menu...
https://www.ilcircolinocittaalta.it/proposte/la-nostra-cucina.html

...and to read about the history of the building, and important role the co-op plays in the welfare of the local community:
https://www.cooperativacittaalta.it
https://www.cooperativacittaalta.it/#aree

The funicular is half way up the hill. Take Bus 1 from the station to the top of Alta.

Thanks for all the feedback!