Paris is a great city, but you may find that all the sightseeing and walking wears out your legs quicker than you think.
On our last few hours however, we took in the lovely Luxembourg Gardens which can be accessed free at several points. It's perhaps not as large as some reviewers seem to indicate, but it is a great size to wander around at your own pace and sit on the free chairs which are scattered around, either in the sun or the ample areas of shade.
The old Palace provides a stunning backdrop to children playing with toy boats on the small boating lake whilst a band played nearby under the trees.
If you are in the area and fancy a short time of reflection away from the busy streets, then take a stroll through here, you will enjoy it.