The deepest sinkhole in Central Europe comes with a grisly tale and an unusual nickname: “The Stepmother Abyss.”

This bar and museum are devoted to the controversial comic book work of Kája Saudek.

The tunnel's elegant proportions keep you snug with no claustrophobia freak-out.

Part modern art project, part traditional chapel, this see-through church is only substantial from the right angle.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

A vast overgrown cemetery, once known as one of London's "Magnificent Seven."