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)

The series of shots show the bare steel infrastructure of the Bushfield army training camp near Winchester which was in operation during World War Two and was used to train Royal Green Jackets recruits in the sixties. The spectacular images were taken by an urban explorer who wished to remain anonymous. Here: A railway siding in Wiltshire, UK where ammunition was transferred by tunnel to an underground storage facility. (Photo by MediaDrumWorld.com)

in WA police cordon guards the house of Poland's ruling conservative party leader Jaroslaw Kaczynski against a crowd protesting a decision by the Constitutional Court, in Warsaw, Poland, on Friday, October 23, 2020. Poland’s top court ruled Thursday that a law allowing abortion of fetuses with congenital defects is unconstitutional, shutting a major loophole in the predominantly Catholic country's abortion laws that are among the strictest in Europe. Defying the pandemic-related ban on gatherings, the protesters chanted for the government to resign. (Photo by Czarek Sokolowski/AP Photo)

A working team appointed by the Archaeological Superintendence of Pompeii performs a Cat scan (Computerized axial tomography) one out of thirty casts of victims of the eruption of Vesuvius in 79 AD in Pompeii, in Napoli, Italy, 29 September 2015. The project which aims to trace the habits of life, employment and social class of the victims, involves a working team of archeologists, anthropologists, radiologists, dentists and engineers to obtain results from the scan. (Photo by Cesare Abbate/EPA)

This February 7, 2018, photo shows João Lousada, a flight controller for the International Space Station, wearing an experimental space suit during a simulation of a future Mars mission in the Dhofar desert of southern Oman. The desolate desert in southern Oman resembles Mars so much that more than 200 scientists from 25 nations organized by the Austrian Space Forum are using it for the next four weeks to field-test technology for a manned mission to Mars. (Photo by Sam McNeil/AP Photo)

A General Atomics MQ-9 Reaper stands on the runway during “Black Dart”, a live-fly, live fire demonstration of 55 unmanned aerial vehicles, or drones, at Naval Base Ventura County Sea Range, Point Mugu, near Oxnard, California July 31, 2015. (Photo by Patrick T. Fallon/Reuters)

Karen Khachanov serves to Carlos Alcaraz of Spain during the Men's Singles Quarter-Final match on Day Ten of the Mutua Madrid Open at La Caja Magica on May 03, 2023 in Madrid, Spain. (Photo by Julian Finney/Getty Images)

The Turkish merchant ship Efe Murat is driven aground in strong winds in Bari, Italy on February 25, 2019. (Photo by De Giglio/Fotogramma/Ropi/ROPI via ZUMA Press/Rex Features/Shutterstock)