Gilmerton Cove
The existence of the Gilmerton Cove, a man-made underground set of chambers and corridors in Scotland, has given birth to various conspiracy theories. The Cover is ornately hand-carved out sandstone, located beneath the streets of Gilmerton–a former mining village turned southeast suburb outside Edinburgh.
There are several theories about the cove’s initial purpose, but none of them have been confirmed. These include smugglers using it as a hiding place, Covenanters taking shelter there, and even noblemen having secret gatherings where they would drink. Gilmerton Cove was featured in the 2007 documentary episode Scotland’s Sin City of Cities of the Underworld on television. This particular show suggests that there may have been a hidden passage connecting the Cove to a nearby Hellfire Club building.