The Velib 'free' bicycle system in Paris is really a great idea. I went for a five day extended weekend with my partner and checked my credit card statement the next month to discover to my delight that I had been all over the city; to the Eiffel Tower, along the Champs Elysees, a scary whirl around Place de la Concorde at rush hour (not recommended for the faint-hearted!) and all over the Grand Boulevards and along the Seine and had spent a massive total of six euros.
The system is user friendly and self-explanatory, you can do it in a range of languages. You tap in your credit card details for a small flat hire rate (no more than five euros, as far as I recall), then hoik the rather clumsy, heavy bikes out of their stand. The bikes are a little uncomfortable and it's important to examine which number bike you'll take before you select at the controls, because some have flat tyres, wonky seats that won't budge, or rattling chains. The bikes have - ostensibly - three gears. These are 'slow', 'slower' and 'snail's cycle-rate' and it can get hairy attempting to belt across a junction will a line of irate Parisian drivers attempting to turn right and cut you up.
If you dock the bike back into another station before 30 mins are up, the ride is free. Interestingly, my partner's credit card statement showed one euro more expenditure so perhaps he had docked in a second or two after me.
However, it's an excellent way to see Paris and a lot of fun.
All over Central Paris
www.velib.paris.fr