A pair of young visitors rushes through a tunnel of colored lights at the annual Garden of Lights display at Brookside Gardens on December, 06, 2015 in Silver Spring, MD. (Photo by Bill O'Leary/The Washington Post)

People enjoy skating at the open air Christmas ice rink on the first floor of the Eiffel Tower after its reopening on December 19, 2016 in Paris The ice rink of about 200 square metres and on the first floor of the tower (57 metres above the ground) is open to the public until February 19, 2017. (Photo by Joel Saget/AFP Photo)

Actress Hiba Abouk attends Hugo Boss night party 2011 on December 13, 2011 in Madrid, Spain. (Photo by Carlos Alvarez/Getty Images)

An Amur tiger walks across a passageway after a news conference at the Philadelphia Zoo, Wednesday, May 7, 2014, in Philadelphia. The see-through mesh pathway called Big Cat Crossing is part of a national trend called animal rotation that zoos use to enrich the experience of both creatures and guests. (Photo by Matt Slocum/AP Photo)

Charlotte fights a monster with a “wand” in her bedroom in Laure Fauvel's “Terreurs”, 2014, in Paris, France. An imaginative photographer has brought to life monsters that haunt children's nightmares. Armed with sticks, wands and swords the eight and nine year-olds appear to be getting the upper-hand against the villains. Parisian photographer Laure Fauvel, 22, said: I wanted the children not be victims and to fight the monsters. (Photo by Laure Fauvel/Barcroft Media)

Revelers dance at a Jacarezinho samba school practice session ahead of Carnival celebrations on February 16, 2014 in Rio de Janeiro, Brazil. The Jacarezinho “favela” was previously controlled by drug traffickers and is now occupied by the city's Police Pacification Unit (UPP). Carnival officially begins February 28, but pre-Carnival celebrations are already underway. (Photo by Mario Tama/Getty Images)

Khan, a five-year-old male White Bengal tiger, looks on inside an open-air cage at the Royev Ruchey zoo in Krasnoyarsk, Russia, October 21, 2016. (Photo by Ilya Naymushin/Reuters)

A walker has left a handprint on a snow- covered tree trunk on Grosser Feldberg mountain in the Taunus mountain range, Germany, 16 January 2017. (Photo by Frank Rumpenhorst/DPA)