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)

Russia's President Vladimir Putin and Saudi Arabia's Crown Prince Mohammed bin Salman are seen during the G20 summit in Buenos Aires, Argentina November 30, 2018. G20 powers open two days of summit talks on Friday after a stormy buildup dominated by tensions with Russia and US President Donald Trump's combative stance on trade and climate fears. (Photo by Marcos Brindicci/Reuters)

Lulu, her Playa name, falls into a foam pit as approximately 70,000 people from all over the world gather for the 30th annual Burning Man arts and music festival in the Black Rock Desert of Nevada, U.S. September 1, 2016. (Photo by Jim Urquhart/Reuters)

A woman looks at head of bluefin tuna on display in front of a store at Tsukiji fish market in Tokyo, Monday, February 19, 2018. The large bluefin are particularly valuable in Japan, where they are considered a premium sushi and sashimi fish. A single fish sold for more than $1.75 million at an auction in Japan in 2013. (Photo by Koji Sasahara/AP Photo)

Danish football fans react to their team's first goal as they watch the UEFA EURO 2020 semi-final football match between England and Denmark on the giant screen in Tivoli in Copenhagen, on July 7, 2021. (Photo by Mads Claus Rasmussen/Ritzau Scanpix via AFP Photo)

Revellers shield themselves as they celebrate in the rain near Stonehenge stone circle, despite official Summer Solstice celebrations being cancelled due to the spread of the coronavirus disease (COVID-19), near Amesbury, Britain, June 21, 2020. (Photo by Toby Melville/Reuters)

Inhabitants of the community of Coyolillo celebrate their Afro-descendant carnival in Veracruz, Mexico on February 25, 2020. This carnival has more than 100 years of history and is the heritage of the African workers who arrived in that area more than 300 years ago to work in the sugar cane fields. (Photo by Hector Adolfo Quintanar Perez/ZUMA Wire/Rex Features/Shutterstock)

A vendor (C) serves customers at a vegetable market as a commuter train passes in Jakarta October 2, 2015. Indonesia's high annual inflation rate cooled in September and should drop more by year-end, but it likely will be 2016 before the central bank can cut interest rates to help an economy growing at its slowest pace in six years. (Photo by Reuters/Beawiharta)