An F/A-18 Hornet assigned to Strike Fighter Squadron One Five One (VFA-151) emerges from a cloud created when it broke the sound barrier in the skies over the Pacific Ocean, July 7, 1999. (Photo by John Gay/US Navy)

A marcher dressed as Marilyn Monroe during the annual Gay Pride march in London, July 1994. (Photo by Steve Eason/Hulton Archive/Getty Images)

In this handout image supplied by the European Space Agency, the Soyuz TMA-03M spacecraft is raised into vertical position on December 19, 2011 at the Baikonur Cosmodrome in Kazakhstan. (Photo by Stephane Corvaja/ESA via Getty Images)

This image obtained January 31, 2017 from the US Geological Survey's Hawaiian Volcano Observatory showing a lava stream, pouring out of the lava tube on the sea cliff at the Kamokuna ocean entry from the Kilauea Volcano on January 29. (Photo by AFP Photo/USGS)

The Mexico – United States barrier – also known in the United States as the border fence, rotted fence or border wall – is actually several separation barriers designed to prevent illegal movement across the Mexico – United States border.

Civilians are led by members of pro-Russian self-defence units as they run outside a military base during an assault in the Crimean town of Belbek near Sevastopol March 22, 2014. Russian troops forced their way into a Ukrainian airbase in Crimea with armored vehicles, automatic fire and stun grenades on Saturday, injuring a Ukrainian serviceman and detaining the base's commander for talks. (Photo by Vasily Fedosenko/Reuters)

A Russian daredevil has captured a vertigo-inducing selfie – while standing on top of a Dubai skyscraper. Nineteen-year-old Alexander Remnev scaled the Princess Tower – the worlds tallest residential building at 1,350ft – before getting his camera out to take these stomach-churning pictures. Photo: He leans on the very top of the tower as he takes this vertigo-inducing picture. (Photo by Alexander Remnev/Caters News)

The Zhangjiajie National Forest Park is a unique national forest park located in Zhangjiajie City in northern Hunan Province in the People's Republic of China. It is one of several national parks within the Wulingyuan Scenic Area.