Avoid the touristic attractions, what else can you do in Paris? Part 1 ( Museums and Galleries )

If you have been to Paris before and done all the sightseeing stuff, then the next thing you probably would think of is  WHAT ELSE YOU CAN DO, I travel to Paris about 5 times a year and every times i discovered more and more things to do, and i am here to share with you. Part 1 (galleries and museums)

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Le Petit Palais
The Petit Palais was built for the 1900 Universal Exhibition, like its neighbour the Grand Palais, on avenue Winston Churchill. It became a museum in 1902. Designed by Charles Girault, it is based on a trapezium shape and is made up of four wings around a semi-circular garden bordered by a richly decorated peristyle. The architect achieved a successful blend of traditional and modern architecture which is evident in the natural flow of visitors around the building and in the bold openings he created onto the Champs-Elysées gardens and inner courtyard garden.
http://www.petitpalais.paris.fr/
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Centre Pompidou
The Centre national d'art et de culture Georges Pompidou was the brainchild of President Georges Pompidou who wanted to create an original cultural institution in the heart of Paris completely focused on modern and contemporary creation, where the visual arts would rub shoulders with theatre, music, cinema, literature and the spoken word. Housed in the centre of Paris in a building designed by Renzo Piano and Richard Rogers, whose architecture symbolises the spirit of the 20th century, the Centre Pompidou first opened its doors to the public in 1977. After renovation work from 1997 to December 1999, it opened to the public again on 1 January 2000, with expanded museum space and enhanced reception areas. Since then it has once again become one of the most visited attractions in France. Some 6 million people pass through the Centre Pompidou's doors each year, a total of over 190 million visitors in its 30 years of existence.
http://www.centrepompidou.fr
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Musee d'Orsay
he museum building was originally a railway station, Gare d'Orsay, constructed for the Chemin de Fer de Paris à Orléans and finished in time for the 1900 Exposition Universelle to the design of three architects: Lucien Magne, Émile Bénard and Victor Laloux. It was the terminus for the railways of southwestern France until 1939.

By 1939 the station's short platforms had become unsuitable for the longer trains that had come to be used for mainline services. After 1939 it was used for suburban services and part of it became a mailing centre during World War II. It was then used as a set for several films, such as Kafka's The Trial adapted by Orson Welles, and as a haven for the Renaud-Barrault Theatre Company and for auctioneers, while the Hôtel Drouot was being rebuilt. The station's hotel closed on 1 January 1973.

http://www.musee-orsay.fr/en/visits/welcome.html