The Grand Canyon Skywalk is a transparent horseshoe-shaped cantilever bridge and tourist attraction in Arizona near the Colorado River on the edge of a side canyon in the Grand Canyon West area of the main canyon. USGS topographic maps show the elevation at the Skywalk's location as 4,770 ft (1,450 m) and the elevation of the Colorado River in the base of the canyon as 1,160 ft (350 m), and they show that the height of the precisely vertical drop directly under the skywalk is between 500 ft (150 m) and 800 ft (240 m).

An Afghan girl carries water on her back as she climbs a hill in Kabul, Afghanistan February 20, 2017. A growing population is straining water supplies in Afghanistan's capital, forcing those who can afford it to dig unregulated wells ever deeper to tap a falling water table. Finding water in arid Afghanistan is virtually always a challenge, but a drop in the groundwater level in Kabul caused by overuse and drought is making it even more difficult for residents, especially the poor. (Photo by Omar Sobhani/Reuters)

A massive positive cloud-to-ground lightning strike hits in Coolidge, Arizona, 31 August 2016. Thousands of rain drops merge to form mammoth travelling sheets of water in these breathtaking monsoons. Veteran storm chaser and photographer Mike Olbinski captured the stunning beauty of monsoons in timelapses and stills while chasing storm systems across America. (Photo by Mike Olbinski/Barcroft Images)

The photography of Art Wolfe covers the globe, capturing landscapes, wildlife, and cultures from every continent; here he talks through a selection of his favourite images. Art Wolfe is an American photographer and conservationist. His photographs have been noted by environmental advocacy groups for their “stunning” visual impact. Here: Snowy owlets (Bubo scandiacus), Arctic National Wildlife Refuge, Alaska, USA. (Photo by Art Wolfe/Art Wolfe Stock)

8 May 2001: Ronnie O'Sullivan of England poses for pictures at the Hilton Hotel with the trophy and his girlfriend Bianca Westwood after winning Embassy World Championship Snooker Final in Sheffield.

A Porcupine on display during the PBS portion of the 2010 Summer TCA Press Tour at the Beverly Hilton Hotel on August 5, 2010 in Beverly Hills, California. (Photo by Frederick M. Brown/Getty Images)

Actress Angelina Jolie (L) and actor Jack Black attend the “Kung Fu Panda 2” photocall during the 64th Annual Cannes Film Festival at the Carlton Hotel on May 12, 2011 in Cannes, France. (Photo by Vittorio Zunino Celotto/Getty Images)

Actor George Clooney from the film “Ides Of March” arrives at the Hotel Excelsior during the 68th Venice Film Festival on August 31, 2011 in Venice, Italy. (Photo by Gareth Cattermole/Getty Images)