American free climber Dean Potter walks on a 41-meter-long and two-centimeter-wide slackline over Enshi Grand Canyon at an altitude of 1,800m on April 22, 2012 in Enshi, Hubei Province of China. Potter successfully finished the lone slackline walk in about three minutes without taking any protective measures. (Photo by ChinaFotoPress/ChinaFotoPress)

Measuring just five feet at its widest point, the ultra-thin home was unveiled in the Polish capital of Warsaw on Sunday, October 21, 2012. Photo: The Keret House is squeezed into the space between two apartment buildings in Warsaw. There's a four-inch gap between the apartment buildings to either side. A perforated steel facade was used to allow in more light. (Photo by Andrea Meichsner/The New York Times)

Two ancient bronze coins, which according to Israel Antiquities Authority archaeologists were struck by the Roman procurator of Judea, Valerius Gratus, in the year 17/18 CE and recently were revealed in excavations beneath the Western Wall in Jerusalem's Old City are exposed to the media' on November 23, 2011 in Israel. (Photo by Lior Mizrahi/Getty Images)

Russian Tu-95MS strategic bombers fly in formation during rehearsals for the Victory Day military parade, with St. Basil's Cathedral seen in the foreground, in central Moscow May 5, 2015. Russia will celebrate the 70th anniversary of the victory over Nazi Germany in World War Two on May 9. (Photo by Tatyana Makeyeva/Reuters)

Two Scottish shorthair cats dressed with red hats are pictured during a cat exhibition in Bishkek, on October 16, 2016. Cat lovers from Kyrgyzstan, Kazakhstan and Uzbekistan took part in the exhibition. (Photo by Vyacheslav Oseledko/AFP Photo)

Paramedics care for a woman who is ill after the Geelong Cup on Geelong Cup day at Geelong Racecourse in Melbourne, Australia, 19 October 2016. The Geelong Racing Club was founded in March 1865 at a public meeting at the British Hotel. The first Geelong Cup was held in 1872 over a distance of two miles. (Photo by Tracey Nearmy/EPA)

Some two thousand runners dressed as Santa Claus make their way through Clapham Common during The London Santa Dash, to raise money for Great Ormond Street Hospital, in London, Britain December 4, 2016. (Photo by Dylan Martinez/Reuters)

A U.S. army soldier exercises in front of a M270A1 multiple launch rocket system as they prepare for a live-fire training exercise of the 6-37th Field Artillery Regiment at a training area near the demilitarized zone separating the two Koreas, in Cheorwon, South Korea, March 9, 2016. (Photo by Kim Hong-Ji/Reuters)