At one moment the scene is everything you expect of Venice; medieval churches, domes and bell towers, and water sparkling in the canal in front of you. But quite suddenly, this picture can be dramatically and controversially transformed.
A colossal, gleaming white cruise ship hoves into view.
At the height of the season, these giants emerging from the sea one after another can bring as many as 30,000 visitors in a single day.
Some resident Venetians bitterly oppose this.
The row about the ships goes to the heart of the controversy over quite how much Venice should give itself over to tourism.