If it's all in a name, this one’ll be enough to make you weep in fear. THE HELLFIRE CAVES.

Interesting fact:

Yikes, scary right? And you don’t even know yet what happened in these caves of hellfire. Well, I can tell you now it isn’t sunshine and lollipops. In fact, these caves in West Wycombe, England, were used by a secret society who indulged in dark rituals, devil worship and much more sordid things that we can’t mention here. The so-called Hellfire Club was dissolved in the late 18th century, but its members are said to roam these dark places, still very much up to no good. You can take a tour if you’re into that sort of thing.