The journey between Frankfurt and Vienna (Wien) is made on board one of Deutsche Bahn's InterCity Express (ICE) services. Two services in each direction travel on/from Dortmund via Cologne (Koln), both good stations for connecting services.
There are also a couple of sleeper train services that are good alternatives to this daytime route, including a EuroNight route between Vienna and Cologne, and another between Amsterdam and Vienna.
InterCity Express:
InterCity Express (ICE) services are high-speed trains linking Germany with a range of other European countries including France, Switzerland, Austria, Belgium and the Netherlands. Services offer both first and standard class accommodation.
Standard class carriages are fully air conditioned, with recliing seats. Seats have fixed or folding tables, as well as luggage lockers. Some special ICE T services allow passengers to sit at the front of the train and take a driver's eye view through a glass partition. First class carriages include power points for mobile phone/laptop charging. Some also feature individual video screens.
ICE trains have a bar/buffet carriage, selling a range of drinks and hot/cold food. There is an at-seat trolley service that travels through both standard and first class carriages.
Passengers are allowed to take two bags/suitcases onboard with them, as well as one piece of hand luggage. Bicycles are also permitted, provided they are in a bicycle bag. Domestic pets may also be transported, with a maximum for two dogs or pet carriers per passenger.