Gilmerton Cove is a series of caves underneath a cottage in the Edinburgh suburb of Gilmerton. It was rediscovered and restored in 2003 and now available to visit. There have also been many studies of the area over the years, including surveys with radar technology. The complex features beds, a fireplace, a forge and many other nooks and crannies
It is not known what the caves were created for but there is reference to a local blacksmith who was reprimanded for allowing people to drink in there on the sabbath in 1769.
Theories about their original purpose include a smugglers hideout, a den of sin, or a secret passage to Rosslyn Chapel and Knights Templar connections. Whatever their purpose they are well worth a look, although you need to book a tour ahead of time.