A mysterious island said to exist off the coast of west Ireland appeared on maps up until the 1865 - yet no one has ever managed verify its exact location.
Reported sightings of Hy-Brasil date as far back as the 1325 and according to Irish myths the legendary island spends most of its time shrouded in mist.
Only for one day every seven years are sailors able to see the island in the Atlantic Ocean.
Like the lost city of Atlantis, the unusually named Hy-Brasil has been subject to many supernatural tales over the centuries across Europe, including accounts of advanced civilisations living on it.
One story concerned Captain John Nisbet who in 1674 reportedly ended up stranded with his crew on Hy-Brasil while sailing from France to Ireland.
On the first day there they found an uninhabited castle and after falling asleep they awoke to find "a very ancient grave gentleman, and ten men following him bareheaded (as if his servants) coming towards the shore, where the ship lay."
The man feasted with the crew and revealed that the island was called "O'Brazile" and that he and several other people had been "tyrannically" locked up in the castle until then by "the malicious diabolical art" of black magic.
The island has also been inhabited by priests and monks possessing formidable ancient knowledge and Irish Saint Brendan's voyage to locate the 'Promised Land' in the fifth century could have been for Hy-Brasil.
The last known documented sighting of the island was in 1872 by Robert O’Flaherty and T.J. Westropp.
The latter said he had visited it three times before and loved it so much that he brought his family along to see the place - where they all reportedly saw the island appear then disappear right in front of them.
The most recent, and perhaps most unsettling, account of Hy-Brasil was a UFO encounter in December 1980.
The Rendlesham Forest incident, as it is known, is thought of as the UK's version of Roswell.
Various unidentified crafts were reported near RAF Woodbridge, a military base being used by the US Air Force at the time.
Sergeant Jim Penniston claimed to have touched one of the flying objects that had landed and then telepathically received a slew of binary codes in his head from it.
He wrote the code down and had it translated, which was said to list the co-ordinates of ancient sites around the world such as the Great Pyramid of Giza.
The location of Hy-Brasil was also included - 52.0942532N 13.131269W - as well as an origin year for the island of '8100'.
Intriguingly, the co-ordinates when entered into Google Maps do take the user to a location in the Atlantic Ocean.
