Extreme window cleaners around the world.

Cleaners abseil down one of the faces of Big Ben, to clean and polish the clock face, above the Houses of Parliament, in central London August 19, 2014. A week has been set aside for the cleaning of what is officially known as the Great Clock, which is set in the Elizabeth Tower.

Window cleaners hang from the facade of Ngee Ann City shopping mall in Singapore January 9, 2014.

A window cleaner passes a lighter to his colleague while rappelling from a new building in Tianjin March 23, 2007. 

Workers suspended on ropes clean the glass windows at the Tornado tower in Doha March 20, 2011.  

Cleaners abseil down the front of a newly constructed building in central Beijing May 3, 2011.

An abseiler secures a giant canvas along the River Thames of a photograph showing Britain's Queen Elizabeth and Royal Family during the 1977 Silver Jubilee, London May 25, 2012. 

Cleaners abseil down the front of a shopping mall displaying the logo of Italian fashion label Giorgio Armani in central Beijing June 26, 2011. 

 A cleaner abseils down the side of a newly renovated building in central Beijing March 5, 2012.

Cleaners open windows as they abseil the front of a building in the financial district of Beijing August 3, 2009.

A worker cleans the window of a building in Bangkok January 22, 2009. 

A worker walks atop the roof of the National Stadium (R), also known as the Bird's Nest, as cleaners abseil down the exterior of the National Aquatics Center, also known as the Water Cube, at the Olympic Green in Beijing July 17, 2008. 

Workers clean the pool surrounding Beijing's National Grand Theatre April 9, 2009 as cleaners remove dirt while abseiling down the glass roof. 

Workers abseil at the top of the Swiss Re 'gherkin' building in London in this January 14, 2004 photo.

Workers clean the exterior of the Oriental Pearl TV Tower during a hazy day at Lujiazui financial district of Pudong in Shanghai, March 10, 2014.