Though there's certainly a lengthy list of stuff to do in Venice, the first stop should be Piazza San Marco, one of the most iconic attractions in Venice and which Napoleon described the most beautiful square in Europe. Piazza San Marco is also home to many of the other top things to see in Venice.
The first and most important is St. Mark's Basilica, a masterpiece of Byzantine architecture. There, you'll also find the Gothic-style Ducal Palace, and the Clock Tower, one of the best places to visit in Venice to get a bird's-eye-view of the city.
Interestingly, among all of the top Venice attractions, a large part of them are palaces. In addition to the aforementioned Ducal Palace is the Ca 'd'Oro, which houses a museum, Palazzo Fortuny by the Spanish painter of the same name, the Palazzo Dolfin Manin, or the Palazzo Grassi, which hosts many different expositions.
Though there are tons of things to do in Venice, don't forget that one of the most charming Venice activities is simply strolling around the city's narrow streets and sampling the quaint canal-side cafes and bridges. If you're still curious about what to do in Venice, have a look on minube and discover great tips and recommendations from real travelers who've been there before.