For starters, the trains are a great way to get around and although we rented a car, I don't recommend at all in any major city. There are also trains that run into smaller towns in the countryside as well (unlike the US), so only use a rental vehicle if necessary. If the rental cost doesnt kill your wallet, the petrol will. Sources tell me petrol is around €1,25/litre. For non-metric folks, thats about $6,25/US gallon. I guess its down from the $9/US gallon over the summer........