From the surface there is nothing special about the hilly countryside around the city of Cankiri in Turkey.However 1,300ft below ground is a stunning salt mine which was first dug by primitive humans around 5,000 years ago.
Despite its incredible age the mine is still in use today and produces more than 500 tonnes of salt each year which is used in cooking and for a range of souvenirs.
According to a 1971-79 survey there is still more than 1billion tonnes of ore left in the mine, which is extracted using machines and underground blasting.
This picture was taken by Melih Sular, 32, who was guided through the caves by Murat Danaci as part of the National Geographic photography contest.
He said: "When I first entered the salt cave I was afraid. I thought to myself: "What happens if it collapses?"
"The cave is cool and scentless, which is because it is a very old salt cave. The walls are all made of rock salt and the texture is varied because of the digging machines used."
While temperatures in the city regularly reach 92 Fahrenheit, the mercury never strays much above 59 degrees inside the ancient caves.
The Hitties were an ancient race who built an empire in the Middle East which covered most of modern-day central Turkey, northern Syria and Iraq and flourished between 1,400 and 1,200BC.
All the ore extracted from the mine, which measures in at around 90 percent purity, is taken by diggers to nearby railway tracks where it is transported to a factory for processing.
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