A tourist walks inside the Ice Palace glacier hollow at Hintertux glacier, located at around 3250 meters above sea level, in Zillertal, Austria, 02 March, 2016. The hollow's temperature remains constant at 0 degrees Celsius, in summer and winter alike, and is also used by the University of Innsbruck for scientific research projects. (Photo by Lisi Niesner/EPA)

Beryl Lipton, left, douses Matt Lee during the ice bucket challenge at Boston's Copley Square, Thursday, August 7, 2014 to raise funds and awareness for ALS. The idea is: pay up for charity or get doused. The fund-raising phenomenon is catching on fast, propelled by popular videos of the dunkers and the dunked – including famous athletes and entertainers – posted on social media sites. And the challenges are raising tens of thousands of dollars and immeasurable awareness for causes from ALS to breast cancer to a camp for kids who've lost a father to war. (Photo by Elise Amendola/AP Photo)

A woman eats an ice cream as people sunbathe on the beach in Barcelona, Spain, Friday, January 26, 2024. Spain's weather agency says recent abnormally high temperatures for this time of year are set to continue in many parts of Spain on Friday and over the weekend, with an almost summer-like feeling in many coastal areas as people take to the beaches to sunbathe and some to have a winter swim. (Photo by Emilio Morenatti/AP Photo)

The picturesque Zao Ski Resort, one of Japan's oldest and most popular ski destinations, is illuminated on February 10, 2007 in Yamagata Prefecture, Tohoku region of Honshu island, Japan. Coniferous trees such as the Aomori white fir lie covered with chrystallised ice and snow (described as “silver frost” or “snow monsters”) and attract visitors. (Photo by Koichi Kamoshida/Getty Images)

A competitor in fancy dress emerges from muddy water during the Tough Guy Challenge endurance race on January 29, 2012 in Telford, England. Every year thousands of people run the 8 mile assault course which involves freezing temperatures, fire and ice. (Photo by Michael Regan/Getty Images)

Construction cranes stand on the Unstrut Valley high-speed railway bridge on March 19, 2012 near Karsdorf, Germany. The Unstrut bridge, which is 2,668m long (about 1.6 miles), is among 38 bridges and 26 tunnels German state rail carrier Deutsche Bahn is building along a new ICE high-speed railroad connection between Nuremberg, Erfurt, Halle, Leipzig and Berlin in a multi-billion Euro project across eastern Germany called the German Unity Transportation Project (Verkehrsprojekt der Deutschen Einheit). (Photo by Sean Gallup/Getty Images)