The birthplace of the modern map has been traced to a building in Edinburgh Castle by a leading historian.
Edinburgh Castle is one of Scotland's leading tourist attractions
Historic Scotland principal historian Chris Tabraham believes the first major map-making project in the 1740s was carried out in the Governor's House.
The project was commissioned by the Army to create the first comprehensive scale maps of Scotland.
Maps were seen by the Army as crucial against Jacobite attempts on the throne and saw troops deployed quicker.
The project was carried out by William Roy and Paul Sandby, whose work laid the foundations for the Ordnance Survey, Britain's national mapping agency.
Mr Roy spent his summers in the field with survey teams, then returned to Edinburgh Castle where he and draughtsman Mr Sandby made the maps in the winter.
Dr Tabraham researched where the pair worked on their maps after being invited to contribute to The Great Map, a book bringing together all the maps the men produced at the castle.
He said: "Roy and Sandby helped transform the way we see and understand the world.
"Their project to systematically map the entire Scottish mainland was such a success that Roy was able to lay the foundations for the Ordnance Survey.
"But that begged the question of where exactly in the castle they worked.
"Find that and you find the spiritual home of OS and all that has resulted from the remarkable work it has done for more than 200 years."
He said it was unlikely that they were based in the military core of the castle complex as they were civilians, but the Governor's House was outside this area.
Their direct boss Colonel David Watson had the storekeeper's lodgings within the Governor's House, and its basement would have provided an ideal space for the mapmaking team.
Another clue is that by 1805 the entire storekeeper's lodgings had been turned into the ordnance office.
It lasted from 1747to 1755 and Roy's boss obtained royal backing for the scheme, which came after Bonnie Prince Charlie's uprising of 1745.
Paula Good, of Ordnance Survey, said: "William Roy is a key figure in the history of OS.
"Unfortunately, he never got to see his vision become reality as he died the year before Ordnance Survey was finally set up."