A woman wears a face mask in the part of the city near neighbourhoods known for burning coal for heating in Ulaanbaatar, Mongolia January 26, 2017. Not many people in Ulaanbaatar wear masks to protect themselves against pollution. (Photo by B. Rentsendorj/Reuters)

A Yorkshire Terrier rests backstage before competing at the 141st Westminster Kennel Club Dog Show, February 13, 2017 in New York City. There are 2874 dogs entered in this show with a total entry of 2908 in 200 different breeds or varieties, including 23 obedience entries. (Photo by Drew Angerer/Getty Images)

A miniature model of Chichen Itza in Mexico, part of Gulliver's Gate, a miniature world being recreated in a 49,000-square-foot exhibit space in Times Square, is seen during a preview April 10, 2017 in New York City. (Photo by Timothy A. Clary/AFP Photo)

High-flying photographer Jeffrey Milstein, renowned for his aerial photos of US cities, snaps landmarks through the open door of a helicopter. This month he hired a chopper in London and amazingly he had just an hour to cover all the buildings he wanted to capture including Buckingham Palace, the London Eye, the glass roof of the British Museum and the Gherkin and Walkie Talkie towers in the City. Here: Jeffrey Milstein captured these stunning images through the door of a helicopter hovering over central London. (Photo by Jeffrey Milstein/Rex Features/Shutterstock)

Base jumpers leap from the 300-metre high skydeck of Malaysia's landmark Kuala Lumpur Tower against the backdrop of the city's skyline on October 3, 2016 during the annual International KL Tower Base-Jump event. (Photo by Manan Vatsyayana/AFP Photo)

Model Inna Magomedova uses her mobile phone while she presents “The Alive Painting” body art work by Russian artist Maria Gasanova during the Art Krasnoyarsk annual festival in Siberian city of Krasnoyarsk, Russia, October 26, 2016. (Photo by Ilya Naymushin/Reuters)

A man in a Donald Trump mask joins hundreds of other protesters and activists as they march during a demonstration near a midtown hotel which is hosting a black-tie fund-raiser for the state Republican Party on April 14, 2016 in New York City. (Photo by Spencer Platt/Getty Images)

A train drives along a field at a salt production site at the Sasyk-Sivash lake near the city of Yevpatoria, Crimea, November 14, 2017. A saltwater lagoon known as Lake Sasyk-Sivash on Ukraine's Crimea peninsula is the source of a rare resource: pink salt. The mineral is tinted by tiny algae that produce the pigment beta-carotene. Each autumn, seasonal workers collect thousands of tons of pink salt for processing and export. (Photo by Pavel Rebrov/Reuters)