Campanile bell tower--you can ride an elevator to the top of the tower for €8. In 1902, the tower toppled and was rebuilt 10 years later.
On the day we visited, it rained for about 20 minutes and the square flooded.
At the top of the clock tower are 2 bronze Moors swinging their clappers at the top of each hour.
Winged Lion, the symbol of Venice, on the clock tower
Electronic clock that changes every 5 minutes
View of St. Mark's Square from St. Mark's Basilica.
Entry to St. Mark's Basilica is free but you have to wait in a long line to get in. Otherwise, you can reserve an entry time online and pay €2 or have a large bag that you can check and bypass the line. You cannot take any pictures inside. The inside of the church is lit from 11:30-12:30 every day and it's worth going at this time. Dress modestly--no bare knees or bare shoulders allowed.
You can visit the San Marco Museum for €5 to see the original bronze horses. These horses are replicas and overlook the square.
Tetrarch statue--at the corner of St. Mark's Basilica nearest the Doge's Palace. The Roman Empire for a time was ruled by a tetrarchy, a group of four rulers. The tetrarchy consisted of 2 Augusti (senior emperors) and 2 Caesars (junior emperors).
Doge's Palace--home of the ruling duke (doge) and seat of the Venetian government for 400 years. Combo ticket, including admission to the Correr Museum, is €19. You can also take the "Secret Tour" of the Doge's Palace for €20 (entrance to Correr Museum not included). You will need to sign up beforehand but you get to see rooms not open to the public.
You'll need to tour the Doge's Palace in order to cross the Bridge of Sighs