I love the variety of gardens in Paris. The museum of the Quai Branly is a very special building surrounded, and even crossed by a very special garden. It is not a botanical garden, but it brings inside a huge variety of trees and bushes. It also has alleys, small hills, places where you can sit or meditate and some special lamps that give it a magical touch in the evenings.
The nicest thing about it is that you can enter for free. This is why I suggest that when you visit the busy streets that lead to the Eiffel tower, full of people posing in the most weird position to have as many followers as possible in the social network, put your telephone in the pocket, walk to the Quay Branly museum and let yourself walk around, sit in one of the relaxing benches and let your soul breathe in this excellent oasis in the center of the city.
You can see more about it in its dedicated site at The Garden of Quay Branly Museum. You can access it from the Quay Branly but also from the side in Rue de l’Universite.