Venice - with St. Mark's Square, the Great Lagoon, the gondolas on the Grand Canal, Venice's Carnival together with great architecture, artistic masterpieces, particular narrow streets, the Biennale, the Marine Republic, but Veneto is not only Venice.
Cortina d'Ampezzo - in the province of Belluno, is part of the Veneto as well. A place with spectacular views of the Dolomites where you can relax and walk in summer and go skiing in winter. The Olympic Wintergames in 1956 helped Cortina d'Ampezzo to become a city known anywhere in the world.
Padova, the ancient and learned city with its Basilica del Santo that houses the relics of Saint Antonio is one of the major attraction points for millions of pilgrims every year.
Verona - The city of Shakespeare's Romeo and Juliet? If you plan to go to Verona you should at least try to get one of the searched tickets for the opera in the Arena.
Get a map of Venice with the water bus routes. You can see major parts of the city just by getting on and traveling the canals around the major islands.
Just sit in St Marks Square and watch the pigeons, listen to the music, watch the people go by.
The Venitian glass is beautiful.
Be careful about the time of year you go to see Venice. It is under water some times. Planks are put out to walk when the sidewalks are not walkable. If you go the right time of the year, it is a beautiful city and well worth the trip.