Paris
Paris is a large city with many of the main attractions spread over the 19 arrondisments. Although there is a great metro system another way to get around cheaply, feel the wind in your hair and smell all that great french bread baking is to rent a city bicycle called a velib.
This is a great system where you purchase a prepaid card or use your credit card to rent the bikes. You only pay for the time you use them.
The bikes are stationed all over the city and it is a simple matter of finding a station releasing a bike and setting off to see the sights. When you arrive you park your bike in the nearest staion. No need to worry about locks and chains. When you have finished at that sight you go back and get a new bike and cycle to you next destination and so on.
The great thing about Paris is that it has many designated bike paths so cycling is relatively safe in the city.They also close the roads around theSeine on Sunday mornings and they become bike only zones.