Dressers make last minute adjustments to the costumes of dancers performing as horses during a press preview of American artist Nick Cave's first major work shown in Australia, entitled HEARD.SYD in Sydney, November 8, 2016. Over several days the live art performance will feature 30 “horses” dancing to live percussion beats in suits made from coloured raffia plant fibres. (Photo by Jason Reed/Reuters)

A model train travels past a scaled model of New York's Grand Central Station built entirely with plant parts during a media preview of the 25th annual Holiday Train Show at the New York Botanical Garden in the Bronx borough of New York City, U.S., November 14, 2016. (Photo by Mike Segar/Reuters)

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).

The Air2 (Air Squared) floating Bluetooth speaker from Axxess CE is displayed at CES Unveiled, the opening event for the media preview days at the 2015 Consumer Electronics Show, January 4, 2015 in Las Vegas, Nevada. The speaker which levitates over its own base is one of the winners for the CES Innovation Awards and is patent pending. (Photo by Robyn Beck/AFP Photo)

Humboldt Penguins swim in their pool as a keeper looks on through a spherical window during the annual stocktake press preview at London Zoo in Regents Park in London Monday, January 4, 2016. A requirement of ZSL London Zoo's license, the annual audit takes keepers a week to complete and all of the information is shared with zoos around the world via the International Species Information System, where it's used to manage the worldwide breeding programmes for endangered animals. (Photo by Alastair Grant/AP Photo)

A member of the Qinghai Acrobatic Troupe checks her hair with a smartphone during a media preview for the world premiere of cabaret show “Shanghai Mimi” as part of Sydney Festival in Chinatown, central Sydney, Australia, 08 January 2019. Sydney Festival 2019 runs from 09 to 27 January and will feature theatre, dance, circus, music, visual arts and talks from international and local artists. (Photo by Steven Saphore/EPA/EFE)

People enjoy the fine weather on the coast at Wembury during the first ever nationwide survey to map the location of the threatened and creatures on March 24, 2011 in near Plymouth, England. Often found on the coast, and particularly in the south west of England, the number of oil beetle species found in the UK has halved in the last 100 years and the survey will help establish the whereabouts of the remaining four species and boost efforts to secure their future. The survey is being launched today by Buglife: The Invertebrate Trust and the National Trust in partnership with Natural England and Oxford University Museum of Natural History. (Photo by Matt Cardy/Getty Images)

A person stands near the “Untitled” installation of miniature elevators by Maurizio Cattelan at a preview of the Postwar and Contemporary Art Evening Sale at Christie's auction house on November 4, 2011 in New York City. The 33-inch functioning elevator installation is expected to realize $400,000-$600,000 at the November 8 auction. (Photo by Mario Tama/Getty Images)