I just came back from a weekend in Venice, and it was so interesting to see the change between day and night @sandra. The days are busy with people, and then it becomes calmer (but not quiet) at night.
A recommendation from me:
I did a food tour on Saturday evening, starting at 17:30. It was approximately a three-hour-long tour that included multiple bars called bàcari, which served Cicchetti and wine. This is a wonderful way to learn more about the city and its unique food culture.
And I made some new friends on the tour. Afterwards, our tour guide pointed us in the direction of a small bar where we were sitting with some locals enjoying Select Spritz. A lovely way to spend the evening 
Highly recommend this evening activity!
