This is the world's oldest zoo and was created in 1794 but later expanded and improved over the next two centuries.
It's a relatively small (but easily accessible) zoo located within the Jardin des Plantes in the 5e arrondissement. According to the official website (
www.mnhn.fr), there are 240 mammals, 500 birds, and 130 reptiles housed at this zoo. It's a great place to take children or just about anyone on a nice sunny day. If you only plan to see the Jardin des Plantes or the surrounding museums (I believe there are two, a national history one and a geology one) and you have lots of extra time, you can just stroll around in the zoo.
Admission charge (for May 2007) was €5 (student rate) although adult rate is €7. I believe it's much cheaper for children. You can buy tickets at one of several entrances.
I would recommend this park to get away from the craziness of the museums and all the busy crowds and just spend a day relaxing in the areas of the beautiful gardens.