Roof-topping enthusiast Daniel Lau takes a selfie with high-rise buildings down below as he stands on the top of a skyscraper in Hong Kong, China on August 15, 2017. A craze that began in Russia has now taken hold in Hong Kong, one of the world's most vertical cities. Mr Lau said he had been inspired by Russian climbers and that he was unafraid of the vertiginous heights he scales. (Photo by ImagineChina/Rex Features/Shutterstock)

Russian President Vladimir Putin visits the Byzantine and Christian museum in Athens, Friday, May 27, 2016. Russia's president is due in financially struggling Greece Friday for a state visit that will include a trip to a 1,000-year-old, all-male Orthodox Christian sanctuary in the north of the country. (Photo by Thanassis Stavrakis/AP Photo)

Alexandr Kudlay, 33, and Viktoria Pustovitova, 28, have breakfast in their apartment in Kharkiv, Ukraine on March 5, 2021. Tired of occasional break-ups, this Ukrainian couple found an unusual solution to stay inseparable. On St. Valentine's Day, they decided to handcuff their hands together for three months and began documenting their experience on social media. (Photo by Gleb Garanich/Reuters)

The Sheep watch the sunset from the top of Cleeve Hill, Cheltenham, United Kingdom on June 22, 2020. (Photo by Jack Boskett/The Telegraph)

“Slow”. A calm cow in the messy streets of Jodhpur. Photo location: India. (Photo and caption by Matthias Troeger/National Geographic Photo Contest)

A British photographer has captured life at the “edge of the world”. Timothy Allen, best known for his work on BBC's Human Planet, trekked through the freezing Siberian wilderness for 16 days as he joined part of an 800km migration of reindeer in the Yamal-Nenets region – a name that roughly translates to “edge of the world”. The stunning pictures feature the nomadic Nenets tribe, who drink blood to survive in -45°C temperatures. Timothy's epic journey, which will be revealed in an eight-minute documentary on Animal Planet USA, saw him travel across the bleak terrain of the frozen Ob River with the Nenets people in December last year. Here: An empty camp is shown beneath a colourful sky in Siberia, December 2016. (Photo by Timothy Allen/Barcroft Productions)

A worker applies colour to strings which will be used to fly kites, by a roadside in Ahmedabad, India, November 23, 2017. (Photo by Amit Dave/Reuters)

“Warming up”. This photo I capture in the early afternoon, the animal species of lemurs fly. Photo location: Sambas, West Kalimantan, Indonesia. (Photo and caption by Hendy Mp/National Geographic Photo Contest)