Derinkuyu Underground City, Cappadocia region 18 mi. from Nevsehir, Turkey. -- It is one of over 200 underground cities discovered in the region, but it is notable for being the biggest & the deepest. With 11 floors & depth of 85m, this ancient city can accommodate anywhere between 3k - 50k people. First excavated during the Hittite times, it was expanded over the centuries, connecting w/ other underground cities via tunnels. It was a hiding place from marauding armies seeking loot & slaves.
Glimerton Cove - Edinburgh. The caves have been inhabited for at least 300 years & various theories exist about what they were used for, among them that they may have been a meeting place for the Covenanters, who were persecuted in the 17th century for opposing religious reforms of King Charles I. Records show they were inhabited by George Paterson, a blacksmith, in the 18th century, but archaeologists say the network could not have been dug by one man & believe they may date back…
This looks like the underground dwelling of the Tuatha de Danaan, or "Children of Danu", the mythological mother goddess of the Irish Celts. Creatures such as leprechauns and other Fairy Folk were known to inhabit these places, particularly under the burial mounds, which were also known as the fairy mounds for that reason.
Škocjan Caves (Slovenia). 'Where Postojna is baroque, the caves at Škocjan are positively Gothic. It’s all about melodrama here – think Jules Verne, Tolkien and Wagner all wrapped into one. Forget crawling in tiny underground spaces: the Murmuring Cave has walls reaching a hundred metres high, while the Cerkevnik Bridge crosses a gloomy chasm with a 45m plunge to the Reka River.' http://www.lonelyplanet.com/slovenia/sights/cave/skocjan-caves
volcanic lightning --- Martin Rietze, the photographer behind the website Alien Landscapes on Planet Earth, is willing to do whatever it takes to get a great photo -- even if that means inching towards a volcanic explosion while scalding lava spews into the air and lightning strikes from dark clouds above.