A Chinese tourist visits the Mutianyu Great Wall covered in snow on February 23, 2021 in Beijing, China. Affected by the new coronavirus (COVID-19), the number of visitors to Mutianyu Great Wall in 2020 dropped by about 60%. (Photo by Lintao Zhang/Getty Images)

The Haʻikū Stairs, also known as the Stairway to Heaven or Haʻikū Ladder, is a steep hiking trail on the island of Oʻahu. The trail began as a wooden ladder spiked to the cliff on the south side of the Haʻikū Valley. It was installed in 1942 to enable antenna cables to be strung from one side of the cliffs above Haʻikū Valley to the other. A building to provide a continuous communication link between Wahiawā and Haʻikū Valley Naval Radio Station was constructed at the peak of Puʻukeahiakahoe, elevation about 2,800 feet (850 m). The antennae transmitted very low frequency radio signals from a 200,000-watt Alexanderson alternator in the center of Haʻikū valley. The signals could reach US Navy submarines as far away as Tokyo Bay while the submarines were submerged.

Tourists enjoy the rare opportunity to walk in water as they visit Badwater Basin, the normally driest place in the US, in Death Valley National Park, Inyo County, California on February 18, 2024. Badwater Basin, an endorheic basin in Death Valley National Park, was flooded by Hurricane Hilary in August 2023 and recent rains in California. It is the lowest point in North America, at 282 feet (86 meters) below sea level. (Photo by David Swanson/AFP Photo)

Open jaws of a Great White Shark Carcharodon Carcharias, South Africa. (Photo by Stephen Frink Collection/Alamy Stock Photo)

Performers Roni, Liv and Becky behind the scenes at Great Yarmouth Hippodrome Circus, England. (Photo by Nick Warner/The Guardian)

Young category winner. Great autumn morning by Fabian Dalpiaz. (Photo by Fabian Dalpiaz/2018 Astronomy Photographer of the Year)

Travis Gerrits of Canada competes during qualifying for the Mens Aerials at the FIS Freestyle Ski World Cup Aerial Competition at Deer Valley on January 10, 2014 in Park City, Utah. (Photo by Mike Ehrmann/Getty Images)