Syrians gather during an evacuation operation of rebel fighters and their families from rebel-held neighbourhoods on December 15, 2016 in the embattled city of Aleppo. A convoy of ambulances and buses left rebel territory in Aleppo in the first evacuations under a deal for opposition fighters to leave the city after years of fighting. The rebel withdrawal will pave the way for President Bashar al-Assad's forces to reclaim complete control of Syria's second city, handing the regime its biggest victory in more than five years of civil war. (Photo by Karam Al-Masri/AFP Photo)

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)

Tip turkey, dumpster chook, rubbish raptor – the Australian white ibis goes by many unflattering names. But it is a true urban success story, scavenging to survive in cities across Australia as wetlands have been lost. Wildlife photographer Rick Stevens captured them in Sydney. Here: Of all the species affected by river regulation in Australia, the ibis is one of the few that has changed its behaviour and moved to coastal cities. (Photo by Rick Stevens/The Guardian)

Participants gather in the Union Square subway station during the annual No Pants Subway Ride on January 8, 2012 in New York City. The annual event is staged by the group Improv Everywhere which encourages people in dozens of cities worldwide to discard their pants while riding the subway. (Photo by Mario Tama/Getty Images)

A tourist watches as the moon passing in front of the sun as it approaches a full solar eclipse in the northern Australian city of Cairns November 14, 2012. (Photo by Tim Wimborne/Reuters)

A boy evacuates to safer grounds at the onslaught of Typhoon Rammasun (locally known as Glenda) which battered the city Wednesday, July 16, 2014, in Manila, Philippines. (Photo by Bullit Marquez/AP Photo)

Lighting from an approaching thunder storm strikes near the shore in Panama City Beach, Fla., on Thursday, July 10, 2014. (Photo by Brennen Smith/AP Photo/The Decatur Daily)

Revelers gather on a commuter train platform of the HVV city public transportation system to drink alcohol on September 30, 2011 in Hamburg, Germany. Thousands of people participated in the event dubbed the “HVV Abschiedstrinken” (HVV Farewell Drink) that was organized through Facebook and is meant to celebrate the last day before a ban on alcohol consumption goes into effect on the city's public transport. (Photo by Joern Pollex/Getty Images)