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)

Aerial view of Skanderbeg Square in Tirana, lit with Christmas decorations and surrounded by an open Christmas market on December 29, 2021. (Photo by Gent Shkullaku/AFP Photo)

Competitors gather backstage as they prepare to take part in the All Ireland Irish Dancing Championships on November 2, 2016 in Belfast, Northern Ireland. The championships take place at the Waterfront Hall over the course of six days with winners qualifying for the World Irish Dancing Finals which will take place in Dublin next year. (Photo by Charles McQuillan/Getty Images)

A tourist stands on the shore of a private beach in Naama Bay, Sharm el-Sheikh, south Sinai, Egypt, Sunday, November 8, 2015. Britain's foreign secretary says airport security in many cities will need to be overhauled if it is confirmed the Russian plane crash in the Sinai was caused by a bomb planted by the Islamic State group or someone inspired by the militants. (Photo by Vinciane Jacquet/AP Photo)

A man uses iron sheet to make noises, as a way of trying to disperse desert locusts that had invaded their farms during the second wave invasion in Kakongo village, in Nuu-Mwingi East, in Kitui, Kenya, 06 February 2021. The second wave invasion of the desert locusts in the country comes at a time where most famers are expecting to harvest their farm produce in the country. (Photo by Daniel Irungu/EPA/EFE)

Hindu devotees watch as a 12 meter (40 feet) high statue of Hindu monkey-god Hanuman is washed during Hanuman Jayanti, the birthday of Lord Hanuman in Hyderabad, India, Friday, April 22, 2016. Hanuman is one of the most popular gods in the crowded pantheon of Hindu deities, and devout Hindus ascribe great strength and valor to him. (Photo by Mahesh Kumar A./AP Photo)

Bangladeshi children from Khan Tea garden posing for photos on March 23, 2022 with their faces painted after adorning with colors like Rainbows on the celebration of the annual Hindu festival of colors, known as Holi festival marking the onset of spring. (Photo by Md Rafayat Haque Khan/Eyepix Group/Rex Features/Shutterstock)

Silver medalist Vivian Jepkemoi Cheruiyot of Kenya and gold medalist Almaz Ayana (R) of Ethiopia during the medal ceremony for the women's 10000m final of the Rio 2016 Olympic Games Athletics, Track and Field events at the Olympic Stadium in Rio de Janeiro, Brazil, 12 August 2016. (Photo by Sergei Ilnitsky/EPA)