Are you taking the overnight train from Paris to Venice? If so, reconsider. It's gotten pretty bad on that route (no more sleepers, only couchettes) and I'd recommend taking day-time trains via Milan or Zurich instead. You could even take the German night train to Munich and a scenic day-train through the Alps. Slower, but trust me, that CDG-VCE train is bad. Pathetic compared to other night trains in Europe.