A woman crosses the street on a foggy morning in Frankfurt, Germany, Friday, October 29, 2021. (Photo by Michael Probst/AP Photo)

A man runs on a small road in the outskirts of Frankfurt, Germany, before sunrise on Tuesday, September 1, 2020. (Photo by Michael Probst/AP Photo)

American actress and singer Vanessa Hudgens in the first decade of December 2022 decks herself out in Michael Kors. (Photo by vanessahudgens/Instagram)

Commuters by with the buildings of the banking district in background in Frankfurt, Germany, Thursday, February 6, 2020. (Photo by Michael Probst/AP Photo)

The sun rises through the thick fog that covers the city of Frankfurt, Germany, Friday, November 12, 2021. (Photo by Michael Probst/AP Photo)

Carrion crows sit on poles around a field on the outskirts of Frankfurt, Germany, early Monday, June 26, 2023. (Photo by Michael Probst/AP Photo)

Master Sergey Suprun uses a portable radio set as he stands near a rotary dredge which works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, Russia October 27, 2015. The Borodinsky colliery, 9 km (5.6 miles) long and more than 100 meters (328 feet) deep, annually produces more than 20 million tons of coal and is considered to be the biggest opencast coal mine in Russia, according to official representatives. (Photo by Ilya Naymushin/Reuters)

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.