“A Double Eagle is a gold coin of the United States with a denomination of $20. (Its gold content of 0.9675 troy oz was worth $20 at the then official price of $20.67/oz). The coins are made from a 90% gold (0.900 fine = 21.6 kt) and 10% copper alloy”. – Wikipedia

Photo: A “Double Eagle” gold twenty dollar coin is displayed above a catalogue picture showing the reverse side of the coin at Goldsmith's Hall on March 2, 2012 in London, England. Nearly half a million of these coins were originally minted in the midst of the Great Depression in the US. Only 13 are known today after the rest were melted down before they ever left the US Mint, sacrificed as part of a strategy to stabalise the American economy. In 2002 a Double Eagle sold at auction for $7.6 million. (Photo by Peter Macdiarmid/Getty Images)

This photographer has made it her mission to change people’s perception of pigeons – focusing on some of the most beautiful of the more than 300 species found globally. Rather than focus on the gray, nondescript birds people usually associate with the term “pigeon”, Leila Jeffreys has instead decided to snap the more vibrant varieties. Whether it be the wompoo pigeon, with its deep purple breast and green wings, or the rose-crowned fruit dove, with its pink head, Jeffreys, 46, gives the birds the same attention she would give a human model. (Photo by Leila Jefferies/Caters News Agency)

Rusting old petrol pumps outside a long-closed rural village petrol station are seen on a minor road near Trowbridge, Britain, October 21, 2016. From art deco apartments in Sussex to a trendy burger bar in London, some of England's former petrol stations are enjoying a new lease of life following creative makeovers. The overhaul opportunities have been created as more than 20,000 stations closed in the United Kingdom over the past 40 years, according to the U.K.'s Petroleum Industry Association (PIC). (Photo by Toby Melville/Reuters)

Global wildlife populations will decline by 67% by 2020 unless urgent action is taken to reduce human impact on species and ecosystems, warns the biennial Living Planet Index report from WWF (World Wide Fund for Nature) and ZSL (Zoological Society of London). From elephants to eels, here are some of the wildlife populations most affected by human activity. Here: The maned wolf is among the large mammals in the Brazilian Cerrado that are threatened by the increasing conversion of grasslands into farmland for grazing and growing crops. (Photo by Ben Cranke/Nature Picture Library/Alamy Stock Photo)

From Tibetan monks playing basket ball with ice thawing high up in the Himalayas, to the pollution that hides behind the Taj Mahal, here’s pick from 60 exceptional environmental photographs, by photographers and filmmakers from 70 countries, that will go on show at the Royal Geographical Society in London from 29 June to 21 August. The winners will be announced on 28 June. Here: Gravel Workmen of Chittagong, Bangladesh, by Faisal Azim. Gravel workmen look through a glass window at a gravel-crushing yard in Chittagong. Full of dust and sand, it is an extremely unhealthy environment for working, but still hundreds of people work here for their livelihoods. (Photo by Faisal Azim/2016 Atkins CIWEM Environmental Photographer of the Year)

Small transportation boats, known as bumboats, leave trails of light as they travel across Marina Bay past the skyline of Singapore in this photo taken in 2004. Singapore holds a Jubilee weekend from 7 to 10 August to celebrate the 50th anniversary of its independence. Fifty years ago, hundreds of small boats lined the Singapore river in the city centre. Today, most small boats are gone, except a handful of neon-lit tourist ferries. Maritime trade is still the backbone of the city-state but after decades of rapid growth Singapore, which at less than half the size of London is among the world’s most densely populated nations, is also a popular tourist destination and a thriving global financial hub. (Photo by Edgar Su/Reuters)

“The Daleks are a fictional extraterrestrial race of genetically manipulated mutants from the British science fiction television series Doctor Who. Various storylines portray them as having had every emotion removed except hate, leaving them with a desire to purge the Universe of all non-Dalek life. Collectively they are the greatest enemies of the series' protagonist, the Time Lord known as the Doctor. Their famous catchphrase is “Exterminate!”, with each syllable individually synthesised in a frantic electronic voice” – Wikipedia

Photo: Max Hardy, aged 6, stands by a street sign from the Doctor Who Experience as Dalek, from the cult television show Doctor Who watches him on April 16, 2011 in London, England. The Doctor Who Experience Exhibition is currently running at Kensington Olympia Two, celebrating the science fiction programme that was originally screened in 1963. (Photo by Matthew Lloyd/Getty Images for BBC Worldwide)

“Ecotricity's Greenbird vehicle, designed and piloted by Richard Jenkins, broke the land speed world record for a wind-powered vehicle in 2009. Greenbird recorded a top speed of 126.4 mph (203.4 km/h), and sustained a speed of 126.2 mph (203.1 km/h) for the required time of three seconds, beating the previous, American held, record of 116 mph (186.7 km/h), set by Bob Schumacher in the Iron Duck in March 1999 at the same location”. – Wikipedia

Photo: Richard Jenkins poses for photographs with the world's fastest wind powered land Vehicle at Science Museum on August 3, 2009 in London, England. (Photo by Dan Kitwood/Getty Images)