Controversial at the time of its creation, the Louvre’s Glass Pyramid has nonetheless entered the exclusive world of 20th-century architectural masterpieces. For the monthly exterior cleaning of the 2,000 m² of glass panels, it became necessary to design a special robot. The operation lasts half a day, on Tuesdays, when the museum is closed. Above all, the windows have to be cleaned of dust from the paths in the Tuileries Gardens. Twice a year, the interior is conventionally cleaned by window cleaners installed in a gondola.