River pirates, murderous bandits, and serial killers used this Illinois cave as their debauched hideout.

A hollow cement depiction of time's inexorable effect on the human body.

About as hidden as can be, this specialty coffee shop is wedged between multi-story buildings at the end of a dark, skinny alleyway in Seoul.

The intended purpose of this unfinished Elizabethan building remains a mystery.

Pennsylvania's highest point is spotted with boulders which were pushed to the surface by nothing but cold.

For over 100 years, this Indiana town has had a tree growing out the top of the local courthouse.

Left untouched since a double murder-suicide in the 1960s, Los Feliz murder mansion remains a neighborhood mystery.

The abandoned coal loading dock is a canvas for unsanctioned art.

"Dark Sky Park" is heaven on Earth for astronomers, one of the rare U.S. locations with no artificial light pollution.