Germany is a real paradise for railfans. They've tried everything there: tram-trains, tram-metros, that hanging monorail-thing in Wuppertal.

The tram-train in Karlsruhe is a hilariously incongruous experience. One minute you're sitting on a classic central-European city tram, trundling through little streets in Karlsruhe, then (as I remember it) the tram suddenly passes through a gate, accelerates wildly, and literally seconds later you're racing across the countryside. Highly recommended.