I’ve been to Venice a couple of times. It’s one of my favorite northern Italian cities because mostly everything worth seeing is within walking distance of each other or a short gondola ride away. If you’re not going on a romantic trip and just wanting to explore, I recommend 2-3 days max in Venice. Outside of gondola rides, make sure you explore St. Mark's Basilica/St. Mark’s Square, The Peggy Guggenheim Collection, & Ponte di Rialto. And just enjoying walking in and out of all the shops and museums while walking around. Pro-tip, if you use Airbnb, book far out so you can get a chance at cheap but gorgeous place off the canals. A lot of the places there can be very run down. Also, compared to other Italian cities, restaurants can be very expensive in Venice but they mostly offer the same thing so look around before choosing a spot.