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 picture made available on 17 July 2015 shows the bright line of the Milky Way above the old oaks at the Rogalin landscape Park in Rogalin village, near Poznan, on the night of 16 July 2015. (Photo by Lukasz Ogrodowczyk/EPA)

Robert Lewandowski of Poland in action against Cristian Romero (R) of Argentina during the FIFA World Cup Qatar 2022 Group C match between Poland and Argentina at Stadium 974 on November 30, 2022 in Doha, Qatar. (Photo by Amanda Perobelli/Reuters)

A Netherlands fan with his face painted is seen in the stand before the match against Poland during UEFA Nations League action at PGE Narodowy in Warsaw, Poland on September 22, 2022. (Photo by Kacper Pempel/Reuters)

A German special anti-tank gun is ready to fire during the army maneuvers in Silesia, Poland, on September 22, 1928. (Photo by AP Photo)

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 shooting star (L, top) is seen on the night sky during the perseid meteor shower in Jankowo, near Poznan, 11 August 2016. The first half of August is traditionally the best time to look out for meteors called “shooting stars”, or perseids which are the leftover dust particles of a comet tail associated with comet Swift-Tuttle. (Photo by Lukasz Ogrodowczyk/EPA)

Policemen guard Poland's Supreme Court as a protester lies on the pavement in Warsaw, Poland, on Thursday, April 22, 2021. A disputed disciplinary body within Poland's Supreme Court is examining a motion that could result in the arrest of a judge who has become a symbol of the fight for an independent judiciary. (Photo by Czarek Sokolowski/AP Photo)