The International Union of Railways (UIC) and DB (German Railways) cashed in on the in on the COP15 Copenhagen climate change talks with a "Train to Copenhagen" in conjunctions with UNEP and WWF.
The train left from Brussels on 5 December, travelling through Cologne and Hamburg (a route I have travelled) then Copenhagen for the conference. The usual train from Brussels to Cologne is the Thalys (using French TGV trains) From there through Berlin to Hamburg , using DB's ICE train.
It was claimed the rain ran on electricity from renewable sources. The renewable claim would be hard to prove and it is likely that at least part of the journey would be made using French nuclear generated power. This is not to say this is not a much more environmentally friendly means of transport that by aircraft, overall.
ps: Models of the Thalys and ICE are popular.