When looking for green in Paris, there are many places to go, but only one that will change your life—one way or another. And that place is Bois de Boulogne.
Established by Louis Napolean over 150 years ago, this park (which is over 2,000 acres) literally carries within it the unexpected. There you can find a hippodrome, two man-made lakes, a massive forest, the famed Roland Garros tennis facility, and much much more.
In Bois de Boulogne, I breathed more deeply than I had for many months (near Lac Inferiour); I was tailed and almost robbed (in the wrong part of the forest); I met a life-for-life (walking through the grass), and lost a set of my hosts keys (near the amusement park). I journaled, napped, explored, and dreamed. That was all in a day's work, #becauseboisdeboulogne. I'll never forget that place.
Bois de Boulogne, more epic than you can ever imagine, if you can get the guts to go visit.
I dare you to.
(Note: For another great Parisian park, you may want to try Bois de Vincennes, the similarly-sized, yet slightly larger, park on the east side of Paris.)