Overcrowding at Louvre triggers enforced online reservation rule The world famous Louvre museum in Paris is urging visitors to book their visit in advance online after seeing a heavy influx this summer. Making reservations online is set to become compulsory by the end of 2019. A victim of its own success, overcrowding has become a problem for The Louvre, which houses the 'Mona Lisa' by Leonardo da Vinci and is the most visited museum in the world. IMAGES AND SOUNDBITES