But what I want to know is how far out one has to go on the Veneto Plain before it stops being marshy and starts being the pretty farmland that the travel guides show me pictures of when I try to find out more about the geographical region. Even the maps I've found that indicate that the region around the edges of the lagoon is marsh are cute illustrated maps and don't give me much by way of scale.
So. How far out onto the plain does the marshy bit around the lagoon go?
Also, is there any particular reason that I couldn't move the whole idea of the city built on islands in a shallow lagoon to a colder climate (like, one where they typically start to get hard freezes and an inch or two of snow in early winter, which all the sources I've found so far say Venice doesn't) and still have it work pretty much the same way that the Venice in our world does? I don't think so from what I've read so far, but I always like to be sure of these things before I get too far in.