The Monet collection at the Marmottan came from Monet's last living descendant. Many of the paintings came from Monet's home at Giverny. There are multiple panels of water lilies along multiple other scenes.
In addition to works by Monet, the museum has an impressive collection of works by Berthe Morisot, an important female contributor to the Impressionist movement. Other items on display include early 19th century French neoclassical paintings, furniture, and sculpture as well as several paintings by Monet's contemporaries including August Renoir.
Check the website for current temporary exhibits.
The museum is approximately a 10-15 minute walk from the La Muette metro station through a lovely park. The surrounding neighborhood is charming with several restaurants, cafes, bakeries, and pastry shops.
Best to go around opening time to avoid lines.