My preference for cruising is to start the cruise in one port and end the cruise in another, so you can spend more time in both port cities. Possible ports for a Med cruise include Rome, Athens, Istanbul, and Venice...depending on the itinerary of the cruise. Another plus is when the ship is docked in the departing port for 2 days. You basically use the ship as your hotel before you set sail, saving some $$$ on hotel costs. However, I usually advise going in at least one extra day early, just in case there are flight delays or lost luggage, or you want to see more. Venice is a very expensive city, so you want to save where you can. Some cruises do a 2 day dock in the middle of the itinerary, too.
Venice is usually on everyone's bucket list. I'm lucky enough to cross that one off the list, as I've been there twice.
Of all the cities in the world, only Paris comes close to matching Venice for beauty and romance.

If you want to get away from San Marco or the Rialto Bridge areas, which are full of tourists, go off into the tangled passageways, which are an attraction, too. Just remember how you got there!
You'll find pretty residential neighborhoods - homes with flower boxes and clean laundry hanging out of the windows. Best places to eat are the little trattorias where the locals go.

There are no cars in Venice and people walk...a lot!!! Venice is mostly narrow canals and streets spread over more than 100 islands, and boat is the major form of transportation. It's kind of funny. We put cars in garages, they put boats in garages.
Piazza San Marco (St. Mark's Plaza) is where you'll find the renowned Basilica di San Marco. Definitely worth going inside for a peak. The Basilica is the primary tourist attraction (during the summer expect to wait in line). Remember, if you aren't dressed appropriately, you will be sent away. Ladies, be sure your knees and shoulders are covered.
There are a
lot of cafes near St. Mark's and it's a great place to people
watch. The cost of coffee at a café vs. "takeaway" coffee is
really pricey. Hey, the view isn't free if you want to sit at a
café! The pigeons also like San Marco -- you may want to wear a hat.
If you're a museum freak,
the best is Gallerie dell' Accademia (Boat Line 82 to Accademia) with Venetian
art from the 14th - 18th centuries.
The Grand Canal is Venice's version of a super highway and runs through the
heart of the city. This is the place to be! You'll find fabulous views of
palazzos (best way to traverse the Grand Canal is via vaporetto, line #1). The
Grand Canal also divides the city; the east side contains the best-known
tourist attractions, while the west is more residential (but this is the area
that has great trattorias (little restaurants that are inexpensive and have
great food) and local shops).

A gondola ride is the ultimate touristy thing to do, and you'll see different views of Venice -- from the tiny canals. Just like taking a van in Rome that can go places a large tour bus can't. Gondolas typically take two to six people, and you pay per trip, not per person. The ride lasts anywhere from 30 to 50 minutes. Negotiate the rate before you get in and plan to shell out about 80-90 euros +/-. Remember, you are traveling in dirty canal water, so there is a little stench. Remember that Venice was built on mudflats and sandbanks. It's only a myth that the canals are open sewers; the smell of the canals is from algae and silt, not sewage.
Don't forget to
explore the islands of Murano and Burano and stop at Torcello to visit the
first Cathedral in Venice. Murano is famous for its glass
blowing. Be sure to watch the glass blowers as they create works of
art. Best place to get some glass, and rather than chance getting it
broken, consider having it shipped home.
Then head to
Burano to see picturesque fishermen's houses painted in bright pastel colors,
and of course to buy some of the famous lace. Be careful. Some Lace makers are becoming rare, so be sure you are getting authentic lace. Some stores sell imported lace if you get my drift. Same kind we can get here from our friends in China or other countries.
Still looking for
more? If you go into Venice a few days early, be sure to head up to Padua
(Padova). Padua is one of the prettiest cities in Italy, with the oldest
botanical gardens in all of Europe. The big tourist attraction is the Scrovegni
Chapel (Cappella degli Scrovegni),
with its priceless frescoes by Giotto. Think
about getting a Padova Card. It lasts for 48 hours, and also offers free travel
on local buses and discounts for additional attractions. You'll find it
at museums and local tourist offices, or online when you are making a booking
for the Scrovegni Chapel. You'll still have to pay the chapel's booking
fee, but the entrance is free and so is public transport around town. But Padua is an easy town to walk around. If you want a map, stop at tourist information next to the
train station.
The Scrovegni
Chapel is between the train station and the city centre. Take the main
street opposite the station and keep straight. Just after a park you come to
the Civic Museums. The entrance is a short way down a side-street. A
little hard to find because there aren't a lot of signs.
While you're in Padua, make time to visit the Basilica of Saint Anthony
is said to rival St. Peter's in Rome.
Ciao!