I learned the answer to this question last week after watching Supersized Earth, a BBC documentary on global cities. The show featured the window cleaning company Cox Gomyl, whose brave workers are tasked with cleaning the Burj Khalifa tower in Dubai, the tallest building in the world.
It takes a team of 36 window cleaners three months to clean the 2,717-foot building, which has 24,000 reflective windows and about 120,000 sq metres of glass.
nomad-hermit 