Carnival, the Rhineland way
After organising a five-day conference on student empowerment in Prague, going to a German carnival felt like the right thing to do. My visa card was eaten by a Prague airport cash machine, so I had to rely on good Samaritans in order to get via Cologne to Jens's apartment in Mainz. Thanks to Hanne in Prague, a Dutch-German couple at the baggage belt in Cologne and an Italian at the airport train station, I was able to raise enough money to get there.
The Mainz name of this tradition is Fastnacht. Since there is a rivalry between Mainz and Cologne about who are best at celebrating, it's probably best to check out the Carnival in Cologne also.
The Rhine-meandering train ride between Mainz and Cologne is also in itself an ok reason to go to the latter.