But now, archaeologists from across the country are hoping to shed light on what could be one of the region's most mysterious – and most significant – ancient monuments.
Three years ago the Forestry Commission revealed that the Friends of Thynghowe group had found a Viking meeting place – known as a "Thing" – in the Birklands, near Worksop.
Such sites, of which there are only a handful in the British Isles, are thought to have been used in the Dark Ages as a landmark where people came together to resolve disputes.
Andrew Norman, from the Forestry Commission, which manages the Birklands, said: "What was once just a bump in the ground has now got lots of people excited up and down the country."
The earthen mound known as Thynghowe, which was first noticed on 19th century maps and then later identified through trawling the woodland landscape, has now been listed on English Heritage's National Monument Record.
New studies have also found the name Thynghowe in an ancient Sherwood Forest book dated to around the 1200s. However, more research is needed to understand the site's mysterious story.
As a result, Nottinghamshire County Council's community archaeology team is set to carry out a topographical survey of the hill in the New Year, after the Friends of Thynghowe made a successful bid for council funding.
At the same time, University College London plans to undertake a magnetometry survey, which can detect buried archaeology by registering anomalies in the earth's magnetic field.
The academics became involved after hearing about the Sherwood Forest site at a conference on Viking sites in Shetland and Orkney earlier this year, which was attended by representatives from the Friends of Thynghowe group.
Mr Norman added: "This is a major effort to unravel more of its secrets."
Thynghowe was discovered five years ago by husband and wife team Lynda Mallett and Stuart Reddish, along with their friend John Wood, who all live in the village of Rainworth.
Ms Mallett said: "My husband and myself own a woodland in Sherwood Forest. A 19th century document came into our hands which described a walk around Sherwood Forest, taking people around a very important boundary.
"We transcribed it and realised this went through our wood and all the way through Birklands as well. We asked the Forestry Commission if we could then go into Birklands and find anything mentioned in this 1816 document,
"One of the most significant places was a place called Hanger Hill, which is described as having two boundary stones and a stone on it. There were also apparently quite a lot of celebrations which took place there.
"When we did our research, having found this place in and amongst all of the trees, we realised Hanger Hill was also a place called Thynghowe, which is a Viking assembly site."
It is thought that Thynghowe may have marked the boundary between the Anglo Saxon kingdoms of Mercia and Northumberland. However, it may date back much further, as "howe" is a term often used to indicate a prehistoric burial place.
Ms Mallett said Thynghowe could date back 4,000 years – which would make it one of the most important sites not only in the region, but in Britain. She said: "It's a highly, highly significant place in Sherwood Forest and a national rarity.
"There are other 'Things' in Britain, but most of them you can't find a written record of. In this case we've found a written record dating back to the 1200s.
"Also, most 'Things' you can't actually see, because they've been built over or they're on private property. With ours, you can actually stand on it and look around and see some of the landscape that was there way, way back in the past."
To shed light on Thynghowe's history, archaeologists are set to arrive in January and analyse mysterious ancient stones in the area, which could be part of the complex or even predate it.
Ms Mallet said: "We need to bring this to national attention and find out as much as we can about this site.
"The more we can find out about it, the more chance we have of making it a scheduled monument, which gives it the highest level protection that we can get.
"We want to make sure local people know all about it. If this site has 4,000 years of history, there certainly isn't another site in Sherwood Forest as significant as this – and everyone in the world has heard of Sherwood Forest.
"To have a site in Sherwood Forest that is of this age, and that is still here, is really quite amazing."