As the name implies, the Orangerie in Paris was originally built as a greenhouse for growing orange trees. The building is located in one corner of the Tuileries garden next to the Place de la Concorde, near the Concorde Bridge.
Since 1927 the Orangerie has been used as an art museum featuring eight very large oil paintings, more like murals covering entire walls, by the impressionist painter Claude Monet (1840-1926).
Monet spent the last thirty years of his life painting mainly the Nymphéas (water lilies) that grew in his garden in Giverny. He made more than 250 of these oil paintings, which are on display at museums all over the world. But in his will he left the eight biggest paintings to the French state for permanent display at the Orangerie.

Side view of the Orangerie
I remember the Orangerie from the last century as being a rather dark and neglected place, but from 2000 to 2006 the building was completely re-designed and renovated, so that now the Nymphéas can again be seen under indirect natural light, as Monet intended.
In the basement there is an impressive collection of paintings from the collection started by Paul Guillaume (1891-1934), an art dealer who was personally acquainted with the leading artists of his day such as Cézanne, Sisley, Monet, Renoir, Gauguin, Picasso, Utrillo and Matisse. On a recent visit I was particularly struck by the many paintings of André Derain (1880-1954), whose work I have somehow overlooked up to now. (Unfortunately I can’t show any examples because photography was not allowed in the Orangerie when I was there.)

The Kiss by Rodin
Outside the Orangerie is one of the many castings of the sculpture The Kiss, one of the best-known works of the French sculptor Auguste Rodin (1840-1917).
My photos in this post are from 2012. I revised the text in 2018.
See also: Rodin Museum in Paris.
Like Albert I sort-of came across the Orangerie by chance, in that we only went in because it was raining, but I thought it was excellent, both the Monets and the other collections. Odd that you couldn’t take photos – there was no problem doing so when we were there (October last year): https://toonsarah.travellerspoint.com/179/
Yes, in the meantime the French Ministry of Culture has imposed a new policy on all (?) French museums, so photos are generally now allowed in the permanent collections as long as they are done without flash, tripod or selfie-stick.
I actually came across the Orangerie by chance and was very impressed. Well worth a visit.