A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

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

The mayor made the declaration in 2004.

A once-booming Mississippi River town with a history of racial violence is now eerie and mostly abandoned.

The site of the first couple's first kiss is commemorated by the most adorable presidential monument ever.

A legal loophole makes it possible to get away with murder within this 50-square-mile section of Yellowstone.

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

Shop of curiosities with a dinosaur museum tucked in its basement.

A speakeasy takes on Chicago's drinking culture.

This shop for all your super spy needs hides an educational secret.

This massive stained-glass masterpiece is thought to be the largest Tiffany dome in existence.

This narrow coastline trail through the dense Kauai wilderness is among the most beautiful and dangerous in the world.

See just what life was like in a 19th-century prospecting town.

A controversial memorial at the place where Captain Cook met his violent end.

A once-glowing grotto at the bottom of Waikapalae Wet Cave.

Doris Duke's lasting collection of Islamic Art, hidden in a Hawaiian paradise.

The island of Lanai in Hawai'i is a paradise for cats and cat lovers.

St. Augustine's record-setting narrow street was designed to protect against pirates.

World's largest college campus includes a wildlife sanctuary and a former movie set on more than 28,000 acres.

Like Mardi Gras, only everyone's a pirate.

One of the largest-ever mental hospitals now sits abandoned, surrounded by 25,000 unmarked graves.

A nude beach alongside a washed-out road.

The world's largest occupied bat houses hold hundreds of thousands of flying mammals.

Visitors flock to see this church tower's unintended feature: It happens to resemble a giant chicken from multiple points of view.