Okay, I got a amazingly cheap flight to Hahn, which is located not far from the Mosel-Valley. Hmmmm.... but how to get around there for not too much money..... So we started to surf around for a good deal on a rental car and we found a great one! We used 'Sixti Car Hire' where you can hire a car (a 'Smart') as cheap as 5 euro a day! You have to read the fine print though, as there are quite a few things you have to pay attention to. But this can be a very cheap option if you don't need the car for a long distance and travel off-season. You can read more details about this care hire in my transportation tips.
