This museum is a huge place, you could easily spend all day exploring it. I suggest starting on the second floor, which has an extensive chronological collection of paintings. It is by no means comprehensive, but does have a good selection of French painters and is strong for Impressionists and modern art.
By that point you'll be ready for lunch. There is a nice (but expensive cafe) on the first floor, or (if you bring your own food) you can eat outside in the peaceful cloisters.
In the afternoon have a good look at the 19th and 20th century sculptures in the old abbey building, then wander round the first floor which has Egyptian antiquities and a varied selection of objets d'art from many different cultures.
An audioguide is included in the ticket price and is informative.
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