What is the best way to get from Heidelberg to Venice. Flights seem limited and trains hard to plan with these two countries, this is for May
It's going to be a long trip. According to the German Rail website, the fastest connection (11 hr) is via the CNL (City Night Line) night train to Munich, then across Bavaria via Ulm and Stuttgart to Heidelberg.
The next fastest way (13 hr) is by ÖBB bus to Villach and trains from there to Salzburg, Munich, Ulm, and Stuttgart.