This's what you want to know. http://en.wikipedia.org/wiki/Donaudampfschiffahrtselektrizit%C3%A4tenhauptbetriebswerkbauunterbeamtengesellschaft

So, in short: You could as well ask what's the largest existing number. In german you can create words as long as you want. If you don't want to talk about a steamboat but about its captain, you can call him the steamboatcaptain. And if you want to talk about that captain's hat, then it's the steamboatcaptainhat. Sounds strange in english, but it's perfectly correct in german. The difficulty with learning german is that, to understand those words, you have to know the words they consist of, otherwise you may get lost...