This museum is a very little-known gem which should require your whole attention. You should put it at the top of your list (after the Eiffel Tower, Mona Lisa and a few others, of course) because:
1) no line.
2) no crowds.
3) humble and precious beauty to be seen.
4) a place which has a purpose and a soul of its own.
This hôtel was built in 1911 by Moïse de Camondo (1860-1935) ("Moses of Camondo", what a name...) as a copy (more or less) of the Petit Trianon (at Versailles). It's a beautiful classical building which was adapted to the modernity and comfort of the 20th century (central heating, bathrooms and an elevator!), all in exquisite taste with an incredible private collection of works of art of the middle and late 18th century which Moïse collected during all his life. After his beloved son, Nissim (1892-1917) was shot down, as an aviator, during the first world-war and his lineage came to an end, Moïse decided to immortalize the name of his son by giving his name to his newly created museum which he donated to the State at his death in 1935.
There's a lot more to be told about this family, and I can also tell you a lot about everyday life in the 18th and 19th century. But, even if you go there on your own, beauty and good taste speak for themselves.
The visit takes a bit more than one hour. Closed on Mondays and Tuesdays.