If you’re in Paris for a longer period of time you may find that you want to get out of town and visit the countryside. There’s plenty of options available. This map includes several possibilities for day and weekend trips from Paris. The most complete section of the map is for Giverny, which is where you will find the Fondation Monet, Monet’s home and gardens.
I was at Giverny in 2014. My time in Giverny and the section of my map devoted to Giverny was inspired by this article in the New York Times. “Finding Solitude at Monet’s Gardens”
If you go to Giverny, do what the article suggests; be the first ones in the door when the place opens. Then visit the house immediately before a line forms for the house. Then you have as long as you like in the gardens. The gardens close to the house are called the “Clos Normand”, a traditional Normandy-style garden. Across the street and accessible via tunnel is the Japanese Garden and Japanese footbridge. If it it feels like you’re walking through a Monet painting it’s because you are.

Buy tickets in advance online. This lets you cut the line, although if you’re there early there won’t be much of a line. Buy the tickets online anyway. And try to visit on a weekday if you can. Here’s the Monet Foundation’s website.
Also at Giverny is the Museum of Impressionsism, which unfortunately was closed for a change-over in exhibits when we were there.
A little further down the road is the town of Vernon, which has some museums, a cathedral and is overall a very cute place to hang out.
To get to Giverny, I recommend you rent a car and drive out the night before and stay overnight in Giverny. You can also take a train to Vernon and then a bus from there to Giverny, but you won’t have as much flexibility in getting around the countryside. You could also bike out from Paris, although I’ve never done this. You could probably do that as a four day weekend or as the first leg on a longer bike tour. If you do this, please write a comment here and let us know how it worked out.
The map shows you some other places near Giverny and some other places you can get to for a day or weekend trip from Paris.