Since 2016 you are able to rent transport bikes for free. First you have to create an account (which is for free). Then you can go to one of the rental stations and get your code for the bike by text message. The first hour is for free, afterwards it will cost 1€/ per half an hour. The locals love those bikes.
Get your bike for free ( for an hour).You can even transport your luggage with those bikes. There is no easier way to get around. The locals love those bikes, especially the kids like it. Cheaper then any other bike rental station.