In the hilly land of northeast Wales in the UK, amateur archaeologists have come across a remarkable trove of stone tools that could date back as far as 4,500 years ago.

The discovery was made over the summer by the Clwydian Range Archaeological Group (CRAG), a community-led team of archaeologists, around the hillsides between Moel Arthur and Penycloddiau. So far, they’ve found nearly 20 of these hand-held tools which appear to be forged from local limestone.

Very unusually, they were discovered at the site of an ancient stream that has since run dry. Live Science spoke to Ian Brooks, an archaeologist acting as a consultant for CRAG, who said it looks as if the tools were purposely buried in the stream, perhaps as some kind of ceremony. He added that these tools appear to be rather unusual.

"I've not seen anything like them before, and I've talked to a number of colleagues who've never seen anything like them," Brooks told Live Science.

“...they all have this characteristic point at one end, which has then been battered – you've got pitting and distinctive damage on the end, so they've been heavily used," he added.

Archaeologists have been poking around in this area since the 19th century. Previous excavations and carbon dating at the site have shown that it was once a hillfort around 2,500 BCE, during the Early Bronze Age. Other digs managed to find burnt stones, most likely used for boiling water and cooking, that date back even earlier, to around 5,000 BCE, BBC News reports. Some analysis has even suggested that human activity could have been taking place there before the introduction of agriculture during the Mesolithic era.

"We're talking about 8,000 years ago," Fiona Gale, Denbighshire county archaeologist, told BBC News. "We think they were hunter gatherers."

"They were the same as us. They had different issues to deal with but their capacity, their brainpower and understanding was the same, and that makes you feel quite humble."

Undoubtedly, this area was the location of a fair amount of human activity over a number of millennia. So, the researchers at CRAG say they are eager to head back to the Welsh hillsides with their tools next year.