Back in 1976, Soviet archaeologists stumbled across a mysterious structure in the middle of the Siberian wilderness - two parallel rows of around 34 bowhead whale bones stabbed into the snow, forming an ancient, morbid walkway.
Located on a tiny island called Yttygran Island in the Bering Sea, just 82 km off the coast of Alaska, the 550-metre-long alley of bones stretches along the shore, giving the site its name - Whale Bone Alley.
The site is made up of 600-year-old whale jaw and rib bones that tower around five metres in height and weigh 300 kg each. The bones are stuck into the ground and propped up by rocks, and archaeologists believe that down the middle of Whale Bone Alley were once huge skulls and square pits containing tonnes of meat.
Nearly 40 years after it was first discovered, scientists still aren't sure who built the mysterious structure and why, but, as the Express reports, the site has now become something of an archaeological tourist attraction. It's Siberia's slightly creepier answer to Stonehenge or the Pyramids.
The leading theory is that Whale Bone Alley was once a shrine and sacred meeting place created by the local Inuits, known as the Yupik, who hunted whales for food. It's believed that it was built around the 14th century, during a temporary ice age that resulted in prolonged winter and food shortages.
Archaeologists believe that these food shortages could have led to conflicts between Inuit tribes, and Whale Bone Alley may have been the one neutral place they could come together to discuss their problems, take part in sacrificial offerings and store their meat in the square pits that once existed between the bone walls.
However, the Yupik people in the region believe that the site was simply a collective centre for the butchery and storage of whale meat.
While further investigation continues into what exactly its purpose was, Whale Bone Alley is now a World Heritage-listed site, and it's drawing an increasing number of western visitors.
"It is the same kind of historical treasure, and means the same for the history of the North East of Eurasia, as Stonehenge or the Pyramids of Egypt," tour company owner and photographer Evgeniy Basov wrote in a blog following a visit in 2013.
"And just like these, more well-known, monuments Whale Bone Alley raises more questions than answers.
It seems there's something about a good archaeological mystery that we just can't resist - and when that mystery involves towering bones jabbed into the ground, well that's even better.
See more images of Whale Bone Alley below: