Back in 2009, a man named Christopher Aitchison visited Tantallon Castle in East Lothian and snapped a photo of the ruins.
The castle, which dates back to the 14th century, is located on a remote headland near North Berwick and was badly damaged in 1651 during an attack by Oliver Cromwell's forces.
Tourists take pictures of the fortress all the time, but Mr Aitchison's image has caused quite the stir - so much so that people are still talking about it 11 years later.
That's because, if you zoom into it, the photo shows a figure in one of the windows, which some believe to be a ghost, reports Edinburgh Live.
Paranormal fans have been divided over what the image really shows for years.
Some say they see a person in the window, wearing a ruff and centuries-old clothing.
Speaking about his photo, Mr Aitchison previously admitted: "I was not aware of anyone, or anything, being present in my picture."
Spooky!
What's even more interesting is that the photo has been tested and it was confirmed that it had not been digitally altered.
So it's not Photoshop!
And before you go thinking it could be a tour guide in costume or some kind of mannequin, those theories have also been ruled out by experts.
Psychologist Professor Richard Wiseman, from the University of Hertfordshire, who studied the picture, said: "The figure appears to be in period costume but we know 100 per cent that Tantallon Castle is not the sort of place that has dummies or costumed guides."
However not everyone thinks the castle is haunted.
Alex Pryce, a member of the Edinburgh Skeptics group, was unconvinced and instead of a ghost from the past, he thinks the person in the window is a woman carrying a shopping bag.
He explained: "When the picture is enlarged, it is quite obvious it is a woman with a carrier bag in her hand and her handbag over her shoulder.
"It is a woman in a pink jacket coming down some stairs with a shopping bag."
What do you think the picture shows? Let us know in the comments below.
Do you have a ghost story to share? We want to hear all about it. Email us at yourmirror@mirror.co.uk
