The holder of half a dozen world records will walk across the Grand Canyon on a steel cable with nothing but the Little Colorado River 1,500 feet below on June 23. With no tethers or safety nets, the walk will be the highest tightrope attempt ever for the 34-year-old, at a height taller than the Empire State Building. Last year, Wallenda, a seventh-generation member of the “Flying Wallendas” family of acrobats, became the only person to walk a wire over the brink of Niagara Falls. Photo: Nik Wallenda walks across a tightrope 200 feet above U.S. 41 on January 29, 2013 in Sarasota, Florida. (Photo by Tim Boyles)

This breathtaking view from the world's tallest building shows a thick blanket of smoggy fog smother Dubai. The mist almost completely covers the huge sculptures which dominate the skyline. And the spectacular view from the Burj Khalifa – standing at a staggering 828 metres tall – shows the city engulfed by the thick fog. And the smoggy fog reaches heights of up to 400 metres as it rises above the impressive skyscrapers in Dubai. (Photo by Bjoern Lauen/Solent News/SIPA Press)

These spectacular pictures show the incredible moment a rare natural phenomenon happens in the night sky. Red sprite lightning lasts only a millisecond and takes place high above a tunderstorm cloud.The breathtaking flashes of light are caused by huge electrical discharges of lightning in the sky. Marko Korosec, 32, was lucky enough to catch these sprites on camera after months of trying. Mr Korosec, from Sezana in Slovenia, took the shots whilst he was following storms in Vivaro, Italy. (Photo by Marko Korosec/Solent News/SIPA Press)

A sign advising to pray for rain hangs above an exhibit area at the 47th Annual World Ag Expo in Tulare, February 12, 2014. About a hundred years ago, when urban water systems were being developed throughout the state, the city of Sacramento wrote protections from metering into its charter, vowing that residents would always have the right to use as much water as they needed. But on Tuesday, the state's top water regulators released a framework for enforcing California's first statewide mandatory restrictions on urban water use – cuts of 25 percent for non-agricultural users ordered last week by Democratic Governor Jerry Brown as a devastating drought enters its fourth year. (Photo by David McNew/Reuters)

Abbas Alizada, who calls himself the Afghan Bruce Lee, poses during a media event in Kabul December 9, 2014. From the ruins of an iconic bombed-out palace above Kabul, the young Afghan man bearing a striking resemblance to kung fu legend Bruce Lee is high-kicking his way to Internet fame, aiming to show another side to his war-weary nation. (Photo by Mohammad Ismail/Reuters)

The British Breitling Wingwalkers, Danielle Hughes and Emily Guilding, soar above the Palm Jumeirah in Dubai at 1,500 feet (460 meters) in excess of 100mp/h, ahead of their Dubai debut performance at the 2014 UIM Skydive Dubai XCAT World Powerboating Series, on Saturday, 13th December 2014. The British team is the only aerobatic formation display team who employ full time wingwalkers and fly their two Breitling-liveried 1930's Boeing Stearman bi-planes at Air Shows and major sporting events around the world. (Photo by Katsuhiko Tokunaga/Breitling via AP Images)