The site was found by three local historians after a treasure hunt.
It started after husband and wife team Lynda Mallett and Stuart Reddish, along with their friend John Wood, came into possession of a 200 year old document.
It described a walk around part of Sherwood Forest which marked an ancient boundary.
They searched for the boundary on the landscape and found a place called Hanger Hill on which stood three stones.
The historians, from Rainworth, researched further and found that the same place was called Thynghowe on a 1609 map.
This was significant.
“A ‘thyng’ is the name of a Viking assembly site while a ‘howe’ is possibly a Bronze Age burial ground,” said Lynda.