Today I am at Manchester Airport awaiting my flight on Lufthansa to Venice via Munich. I have never been to Italy before and until recently would have considered Venice to be a difficult place to visit for a wheelchair user, but research on the internet seemed to suggest otherwise. In the map on the right those areas marked in green are supposed to be fairly easily accessible, those in khaki less accessible, and those in red not accessible. During the next two days I will find out.
Venice has a system of waterbus (Vaporetto) routes that get you around all the islands and they are very wheelchair friendly. The biggest boats, like the one in the photo to the left, run on routes  and  and display the blue wheelchair symbol. There are smaller boats on other routes which I did not see the symbol on but I managed to use every one that I tried and the crews on them were very helpful.