Hundreds of "witches’ marks" have been discovered carved into caves on the border between Nottinghamshire and Derbyshire – with some thought to signal a supposed entrance to "hell".
The marks are intended to stop evil spirits, say experts, and are thought to be the largest collection in one place in the UK.
Witches’ marks are most commonly found in old churches and houses, often near windows, doorways and fireplaces to ward off from evil spirits.
They are also known as "apotropaic" marks, from the Greek word apotrepein, "to turn away".
The marks were found in the caves at Creswell Crags – one of which is rumoured to have once provided a hide out for Robin Hood – and were previously thought to have been graffiti.
The most common include the double "VV" etchings, thought to refer to Mary, Virgin of Virgins, while there are also diagonal lines, mazes and boxes – intended to capture or trap evil.
The marks appear to have been added to over time.
That may indicate the desire to strengthen protection against evil spirits in response to death, unexpected sickness and poor crops, say experts.
Hundreds of marks were found in just one of the caves at Creswell Crags, which also contains Britain’s earliest cave art: 13,000-year-old pictures of birds, deer, bison and horses.
One collection of marks, carved around a four-foot round hole in one of the caves, is suggested to warn of an entrance to an "underworld".
Paul Baker, director at Creswell Crags, told the Daily Telegraph: "I think over a period of time this hole was blamed or associated with a series of events, illnesses or crop failures to the point in which they hoped the marks would protect them.
"But they clearly felt that whatever was inside it was so powerful that they had to keep going back to add more and more marks.
"Just when you think Derbyshire can’t throw anything else at you, it gives you The Blair Witch Project."
John Charlesworth, the tour leader at the time of the discovery of the marks, said: "The people who made the marks may have thought the big hole was some kind of door to the underworld of even a demon prison, but they were certainly worried about what was going to come out of it.
"You could think of the witch marks as worry lines that demonstrate the anxieties of the time.
"These marks are a kind of folk magic and the hole in the ground may have represented some kind of Pandora’s Box.
"These witches’ marks were in plain sight all the time. Being present at the moment their true significance was revealed will stay with me forever."
The previous biggest find of witches’ marks in caves was 57 in Somerset.
Duncan Wilson, chief executive of Historic England, said: "Even 200 years ago, the English countryside was a very different place; death and disease were everyday companions and evil forces could readily be imagined in the dark.
"We can only speculate on what it was the people of Creswell feared might emerge from the underworld into these caves."
Tours of the caves containing the witches’ marks will start for the first time in late February.