Having just returned from my fifth trip to Venice - but the first for nearly a decade - I feel compelled to say something about a timeless place that is so well known and so well reviewed that it is impossible to offer an original thought in appreciation. Anyway, here is my personal restatement of what others offered in the past: There is no place in the Western Hemisphere that continues to fascinate me as much as La Serenissima, and no other place that I believe is as rewarding when explored on foot.

If you are not an avid urban walker, you can still enjoy all of the top sights in Venice, since the vast majority of them are next to or within a short walk of a vaporetto stop - Linea Uno by itself puts you in touch with practically every major point of interest (hint: buy a multi-day pass, which starts saving you money on your 3rd trip per day on average).

But you will miss a lot if you do just that. Hit all of your major targets, by all means, but also find time to wander aimlessly around the city. The real charm of Venice is found away from tourist crowds. Forget about the map for a while, walk where your whims take you, retrace a few steps when faced with a canal without any means to cross, linger where you feel like it - I would strongly argue that along with seeing its top museums and palaces, getting lost in the city is the unmissable part of a visit to Venice.  

In my case, I easily filled over a week with a mix of aimless wandering and stopping by practically every museum or church of note. If all you did was go to Piazza San Marco and the Rialto Bridge and ride on the vaporetto, you definitely checked off Venice from your list. But you need to go back to see it.