The Louvre, a former fortress and royal palace, is one of the world’s most awe-inspiring museums, a trove of history from the seventh century B.C. to the mid-19th century. Antiquities from the East and West vie for attention with masterpieces by Leonardo and Vermeer; wander aimlessly through its maze of galleries and you’re as likely to stumble into an imperial ballroom as a chamber containing a sphinx. It would take you about three full days to visit every room in this museum. (We know, because we did it.) But don’t worry, we’ll help you make your trip unforgettable, but also manageable.