I should imagine it would be the Orient Express and and as the final scene is in Venice - I'm guessing Venice Station - pure guess though but it would make sense.
It is the VSOE Venice Simplon Orient Express, not to be confused with our version of the Orient Express (also nice). The station used was Budapest. The moving transit shots were along the Rhine between Vienna and Budapest.
If you're a hopeless romantic, it is THE way to travel!
smile