NO-ONE truly knows how old they are, why they were made or what they mean, but stones bearing cup and ring marks are found all over Scotland.
This week the National Trust revealed that the latest collection of cup and ring marks had been found on a stone near the summit of Ben Lawers in Perthshire.
The markings, which could be anything from 3,000 to 5,000 years old, were found by amateur archeologist George Currie.
Mr Currie, a musician who lives near Dundee, has discovered about 500 examples of rocks bearing cup and ring marks on his expeditions around Scotland. But few are as complex and large as the Ben Lawers' example.
He said: "I find them fascinating. They can be 5,000 years old. There is no way we can tell what is going on, but it is obviously something very important to the people who made them.
"They are very mysterious. It is like a message from thousands of years ago."
Mr Currie published his description of the stone in the latest issue of Discovering and Excavating Scotland. He used a global positioning system to ascertain the exact co-ordinates – which alerted the NTS to the discovery on its property.
NTS archeologist for the west of Scotland Derek Alexander said there was a great interest in cup and ring marks.
"There is always going to be a debate about what these things mean.
"They seem to lie on boundaries, so they could be a way to place people in a location. There are also suggestions they are maps of the stars, maps of burial grounds or tribal symbols."