Walking around Paris, we kept seeing these fancy looking bicycles. We wondered if they were electric powered or something. Turns out that they are rentable bikes that can be gotten at various self-serve stations around central Paris. According to our guide on the Context Tour, the bikes were part of a deal between the city of Paris and an advertising firm in return for a monopoly on billboard advertising. They looked to me to be extremely heavy, but Paris is relatively flat, so I suppose they're OK. Unfortunately they can't be rented with most American credit cards (they need something called an EMV chip embedded in them, which the US hasn't widely adopted, but most of Europe has).

More information on Vélib' Paris Velo Rent-a-bikes is here.