Oh, I also recommend you to walk "into" the city. Say, from Piazza San Marco, start walking through the narrow streets and get to see the little stores and nice restaurants they have there, it's quite a nice experience. Just make sure you do it in the right place, otherwise you'll see nothing but houses hehe, and it's also quite easy to get lost since there are tons of little streets and you'll often find that you can't cross to the other side because there's a canal in between. It can get a bit frustrating haha.