The Louvre wasn't always a museum. It started out as a fortress over 800 years ago, then became the home of French kings and queens for hundreds of years. After the royals moved out to Versailles, it was turned into a museum so the public could see all the art they had collected.
There are over 600,000 objects inside - paintings, statues, jewellery, mummies, ancient pottery and even old armour. Only about 35,000 are out on display at any one time, and the rest live in storage. The whole building covers about as much ground as 14 football pitches.
The most famous painting in the world is here: the Mona Lisa, painted by Leonardo da Vinci around 500 years ago. She is much smaller than people expect - only about 77 cm tall, around the size of a school bag. About 20,000 people queue up to see her every day. She has her own special wall, behind thick bulletproof glass.
The big glass pyramid out front was added in the 1980s as a modern front door. People argued about it for years (some loved it, some thought it ruined the old palace) - but now it is one of the most recognised shapes in Paris, almost as famous as the building itself.