Traffic police stand at the side of a road in Pyongyang on November 25, 2016. (Photo by Ed Jones/AFP Photo)

A traffic light is seen next to the Pink Supermoon in Frankfurt, Germany, April 8, 2020. (Photo by Kai Pfaffenbach/Reuters)

Cars slowly move along a bridge in traffic jam in central Moscow, Russia on December 11, 2018. (Photo by Yuri Kadobnov/AFP Photo)

Tara West signals to her partner Natalie Cook during the Bronze final match during the Australian Beach Volleyball Championships at Glenelg Beach on March 13, 2011 in Adelaide, Australia.

A member of the German wireless police picks up signals on the radio equipment he carries on his back, while his colleague takes notes. (Photo by General Photographic Agency/Getty Images). Circa 1925

A man wearing the traditional Carnival Neapolitan mask of Pulcinella performs on Via Caracciolo avenue in Naples, Italy, Saturday, November 14, 2020. The regions of Campania and Tuscany were designated red zone on Friday, signaling the dire condition of a hospitals struggling with a surge of new admissions. (Photo by Gregorio Borgia/AP Photo)

This aerial picture taken on the night of November 12, 2018 shows traffic on an elevated intersection in downtown Shanghai, China. (Photo by Johannes Eisele/AFP Photo)

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.