Željava Air Base, situated on the border between Croatia and Bosnia and Herzegovina under Plješevica Mountain, near the city of Bihać, Bosnia, was the largest underground airport and military air base in the former Yugoslavia, and one of the largest in Europe. (Photo by Thomas Windisch/Exclusivepix Media)

A worker looks at Spring Festival decorations ahead of Chinese Lunar New Year festivities in Beijing, China on January 12, 2023. (Photo by Thomas Peter/Reuters)

Commuters ride on the roof of a Jakarta state rail train at Cawang train station on January 27, 2012 in Jakarta, Indonesia. (Photo by Ulet Ifansasti/Getty Images)

A woman chops a fish at her stall as a train passes by at a morning market near Duri train station in Jakarta in this February 12, 2009 file photo. (Photo by Reuters/Beawiharta)

Mamoni Mandal, member of the Rapid Action Force (RAF), attends a training session at a police training school in Kolkata April 15, 2007. (Photo by Parth Sanyal/Reuters)

Indian army training cadets perform “Kalaripayattu”, an ancient martial art from Kerala, during a combined display ahead of their graduation ceremony, at the Officers Training Academy (OTA), in Chennai, India on September 8, 2023. A combined display of training proficiency was organized at the OTA as a prelude to a passing-out parade of cadets. The combined display marks the culmination of the adventure training and showcases the skills and expertise of armed forces display teams. (Photo by Idrees Mohammed/EPA/EFE)

Sumo wrestlers of Nishonoseki clan appeal to the winner of a training bout for the next opponent during a joint training session ahead of the May Grand Sumo Tournament in Tokyo May 2, 2015. (Photo by Toru Hanai/Reuters)

People train parrots during a parrot-training show held by Kuwaiti bird lovers in Jahra Governorate, Kuwait, December 7, 2020. (Photo by Xinhua News Agency/Rex Features/Shutterstock)