Lonely Planet review for Bycykler
Long before Paris got in on the act of free bikes, Copenhagen had its famous Bycykler, allowing anyone to borrow a bicycle for free. In all there are over 1000 bikes available from 1 May to 15 December.
These gearless bicycles are rudimentary and are certainly not practical for long-distance cycling, but that's part of the plan - use of the cycles is limited to the city centre. To deter theft and minimise maintenance, the bicycles have a distinctive design that includes solid spokeless wheels with puncture-resistant tyres. The bikes can be found at 110 widely scattered street stands in public places, including S-train stations.
The way it works is that if you're able to find a free bicycle, you deposit a kr20 coin in the stand to release the bike. When you're done using the bicycle, you can return it to any stand and get a kr20 coin back.