A must for Van Gogh fans in particular - the collection of works here is small but first-class - and there are many other famous artists represented here as well.
A museum card is highly recommended if you're paying a visit - you get to skip the main queue for tickets. If you don't have one, adult entrance is 7 Euros, and don't forget it's closed on Monday. There's late opening on Thursday evenings.
For more information, check out the excellent museum website at www.musee-orsay.fr.
