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, canals , the Biennale art exhibition and the Venice Film Festival.
Padova, the ancient and learned city with its old University, its botanical garden (a Unesco World Heritage Site), and the Basilica del Santo that houses the relics of Saint Antonio which is one of the major attraction points for millions of pilgrims every year.
Verona - The city of Shakespeare's Romeo and Juliet and a Unesco World Heritage Site. Rich in history and heritage dating since the roman times such as world-famous roman Arena.
Vicenza - the city of Palladio and a World Heritage Site. Home to beautiful Renaissance buildings such as the world famous Villa la Rotonda and the oldest covered theatre in the world Teatro Olimpico.
Treviso - less known but still a very charming medieval town with some canals and great art and architecture.
Rovigo - small but quite pretty city centre, overlooked by many visitors.
Belluno - small town located at the doorstep of the Alps, a good starting point for mountain trekking.
Palladian Villas - a Unesco World Heritage Site comprising many Renaissance villas built by the famous architect Andrea Palladio and scattered throughout the Region.
Dolomites - a spectacular mountain range covering the northern part of the Region, a perfect place for skiing and hiking and also a Unesco World Heritage Site.
Cortina d'Ampezzo - located in the province of Belluno. A place with spectacular views of the Dolomites where you can relax and walk in the summer and ski in the winter. The Olympic Wintergames in 1956 helped it become a city known around the world.
Riviera del Brenta - a riviera filled with beautiful villas overlooking the Brenta canal running from Padova to Venice.
Lido di Venezia 10 minutes from Venice, the golden beach and summer retreat for many Venetians.
Bibione - seaside town popular among locals and tourists.
Jesolo - large seaside town close to Venice, popular among italians and foreigners. Offers a good nightlife with famous clubs such as Il Muretto.
Euganean Hills - a volcanic group of hills, home to various quaint little historic villages, monasteries, churches and villas.
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, and watch the people go by.
The Venetian 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.
Find a website that actually has some information on what to do, not just idle observations and activities that you can do anywhere.