Stunning silhouettes under European cities reveal the size and splendor of the continent’s urban foundations. Photographer and content-manager Anna Arinova, 28, from Moscow, captured the awe-inspiring labyrinths in Russia and Germany. Here: Regenwurmlager, Poland. The Regenwurmlager is an extensive underground fortification area constructed by Germany in 1920s-1940s, now in western Poland, near the city of Międzyrzecz. (Photo by Anna Arinova/Caters News)

A young woman wearing no trousers hits the ski slopes at a ski resort in Xuzhou, in east China's Jiangsu province on January 13, 2015 in a promotional effort to equal “No Pants Subway Ride”, which was marked on January 11 this year. The promotional “No Pants Subway Ride” stunt on January 11 was held as commuters in some 60 cities around the world braved public transportation in their undies, which has gone global since its first staging by US group Improv Everywhere in New York in 2002. (Photo by AFP Photo)

Air National Guard takes to the skies over Puget Sound during Seafair 2015 on Thurs., July 30, 2015 in Seattle, Wash. (Photo by Matt Mills McKnight/AP Images for John Klatt Airshows, Inc.)

Skiers and snow boarders descend from a slope as they attempt to break the record for mass skiing in swimming suits at Rosa Khutor resort near Sochi, Russia, April 9, 2016. (Photo by Kazbek Basayev/Reuters)

A British Spitfire and an American P-51 Mustang from Ultimate Warbird Flights take to the Northamptonshire on August 14, 2020 skies to mark the 75th anniversary of VJ Day. (Photo by Richard Pohle/The Times)

A dog wearing ski goggles rides on the back of a man as they both stand in Times Square in New York, USA on January 25, 2021. (Photo by John Angelillo/UPI/Rex Features/Shutterstock)

The Patrouille Suisse jets perform prior to the Men's Downhill race at the Fis Alpine Skiing World Cup in Wengen, Switzerland, 15 January 2022. (Photo by Jean-Christophe Bott/EPA/EFE)

Italy's Federica Brignone's helmet is seen after their run at the FIS Alpine Ski World Cup in Garmisch-Partenkirchen, Germany, on January 25, 2025. (Photo by Gintare Karpaviciute/Reuters)