We took the overnight train from Paris to Venice, which is much more romantic than it sounds, especially when you bring a picnic dinner of cheese and sausage that ferments in your little compartment.  And they wouldn't let us tube down the canals, so we had to take a gondola.  But we had a great time wandering around the town, down the little streets and across the bridges with no real destination in mind.  And the Ferrovia, or water buses, are a trip!
One truly American note:  just when you think we live in a high-tech global village, you discover something that show you otherwise, like a chamberpot in your train compartment, or no touch-tone phones in the hotels.

Now for Florence