erj:

Hy-Brasil is a phantom island which features in many Irish myths. The island is said to be cloaked in mist except for one day every seven years, when it becomes visible but still cannot be reached. It appears on a map in 1325 off the south west coast of Ireland. Despite the failure of so many attempts to find it, there exist sketches of this island, circular in shape with a river running east to west across its diameter.

If you’re in the Uk listen to this short story piece, written and narrated by Paul Evans, it’s beautiful.

http://www.bbc.co.uk/iplayer/episode/b01mdg51/HyBrasil/