1 Monty: So how is this lock so tricky?
2 Minnesota Jones: The combination is never the same twice, and is concealed by a means so devious as to send men into a gibbering descent into insanity.
3 Monty: Well here's an inscribed brass plaque. That's a start.
3 Prof. Jones: What does it say?
4 Monty: {reading} "A train travels south from Venice at 25 mph. Half an hour later a train leaves Florence, travelling north at 35 mph..."

It's part of the plot. Don't worry. Trust me.

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2017-08-30 Rerun commentary: And yes, there is a train station in Venice, despite Venice being built on a group of islands.

Santa Lucia Station in Venice is connected to the mainland by a railway bridge. The railway bridge doesn't seem to have a Wikipedia page of its own, but it runs parallel to the Ponte della Libertà road bridge, from the mainland urban centre of Mestre to the main islands of Venice.

Mestre is actually considered part of the city of Venice - kind of the suburbs away from the historic centre of the city.