The Louvre is like no other museum in the world, which is why visitors line up early and long, particularly in the summer. Booking a tour may help you jump line. Some of the world's most famous paintings and sculpture can be found in the rambling museum. Probably the most famous is the Mona Lisa, but if you get close enough to see her, you may be surprised to find she's no bigger than a family portrait. The main entrance to the museum is through the strikingly modern glass and metal pyramid by I. M. Pei in the courtyard. Oct. - Mar. free on the first Sunday of the month.