At first glance it looked like a bundle of rags, scrunched up into a ball, encrusted with dirt and eaten by insects.
It had been stuffed up a chimney as a makeshift draft excluder and was discovered during the renovation of a house in Aberdeen.
But when conservation staff at the National Library of Scotland took a closer look, they discovered that the bundle of rags was in fact a rare, late 17th century map by the celebrated Dutch engraver Gerald Valck and published by London mapmaker George Wildey.
Thought to date to around 1690, the large 2.2m x 1.6m wide map features images of William III and his wife Queen Mary II, the joint
monarchs of England, Scotland and Ireland.
There are only two known copies of the map in the world. A similar map from the same period can be seen in the famous painting by Vermeer, Painter in his Studio.
This one was likely to have been owned by someone of importance and would have been hung on a wall for visitors to admire.
The owner remains a mystery, as does the identity of the person who delivered the map to the museum in a poly bag.
This feature was originally published in 2017.