THEY have lain unnoticed for decades despite being walked over by hundreds of pairs of feet every day.
Now, the unusual setts at Forrest Road are to be commemorated by a new bronze plaque after it emerged they were actually specifically laid down to mark the line of the Flodden Wall.
Local historians have been aware of the setts for years but their origins and real meaning was never recognised until now.
The significance of the setts, which line the pavements between Greyfriars Kirkyard and the lane leading to the National Museum of Scotland, was realised by local historians and members of the Old Edinburgh Club.
They made the discovery while researching the history of the Flodden Wall as part of their centenary year celebrations.
They have decided to mark the finding by commissioning a 1000 bronze plaque which will be unveiled tomorrow.
Historians have also retraced the footsteps of the Old Edinburgh Club's first "ramble" in 1908. It was a walking tour around the remains of the city walls – the 15th century King's Wall, the 16th century Flodden Wall and the 17th century Telfer Wall.
Historian Graeme Cruickshank – a member of the Old Edinburgh Club – has been trying to find out the origins of the setts marking the line of the Flodden Wall.
He said: "What I understand is that someone from the council put them down a few decades ago.
"The council records are very patchy and no-one that I've spoken to seems to know anything about them.
"Thousands of people walk over them every day and don't know what they're for. I have seen them hundreds of times and didn't know what they were and now after 30 or 40 years of walking over them I finally know."
Mr Cruickshank, who also runs Edinburgh Historical Enterprises, has led groups of people on tours round the old city walls as part of the celebrations marking 100 years of the Old Edinburgh Club.
He had the idea after reading the first ever minutes of the club which revealed their first excursion was this tour of the city.
In 1908, members started at the Castle Esplanade and went down Victoria Street, along the Grassmarket, up The Vennel, through Greyfriars, down Drummond Street and The Pleasance and along to the old Nor' Loch.
Mr Cruickshank did his best to follow the original route but was blocked from time to time by new buildings that didn't exist in 1908 – and because the Esplanade was closed due to a Boyzone and Girls Aloud gig.
Sections of the Flodden Wall – which was built in response to the threat of an English invasion in the 16th century – were unearthed earlier this year by workers revamping the Grassmarket.
Mr Cruickshank called the discovery of the previously uncovered section as a "happy coincidence" as it coincided with the club's celebrations.
Bridget Stevens, one of the organisers of the ceremony, said the discovery of the significance of the setts is "worthy of an Ian Rankin mystery".