When tinfoil hats aren't enough-- the Gateway to Hell.

[Taltarzac725]

Gateway To Hell: Israeli Scientists Explore Twins Cave For Ancient Door To Underworld (http://www.huffingtonpost.com/2012/04/20/gateway-to-hell-israel-twins-cave_n_1435320.html)

Now this would be a cave to investigate.

[Raen Dear]

I think Doc Savage, the Man of Bronze, once had an adventure in this cave.