High up in the Himalayan mountains lies a mysterious and macabre spectacle - a lake filled with skeletons.
Known as Roopkund Lake, this intriguing enigma is situated 16,500ft above sea level in India's Uttarakhand region on the border with Nepal.
Once a year, when the snow and water sufficiently recede, the lake reveals its contents - a huge pile of skeletal remains believed to be those of more than 500 individuals.
First discovered in 1942, these unidentified skeletons are now thought to have belonged to people from several different parts of the world and have been dated back up to 1,200 years.
DNA testing has also shown that, surprisingly, around one-third of them were from the Mediterranean - many thousands of miles from the Himalayas.
Exactly what happened to them and how they ended up here, however, remains unclear.
"It may be even more of a mystery than before [the skeletons were DNA tested]," Harvard geneticist David Reich told The Atlantic.
"It was unbelievable, because the type of ancestry we find in about a third of the individuals is so unusual for this part of the world."