An artificial hill and apparent calendric structure built in the Early Middle Ages immortalizes a legendary Polish princess.

An emerald-green grotto just a short trip from Austin.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

On Japan's Tashirojima Island, cats are king.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

A forensic lab dedicated to fighting crimes against wildlife.

The "original web site," this farm in Northern Vermont encourages orb-weaver spiders to build their daily webs, and then sells the preserved masterpieces.

An otherworldly restaurant perched on the edge of a jagged cliff next to a medieval holy city.

Dramatic sea stacks adorn the coast of this small village on the Adriatic coast.

Some of the smallest works of art in existence.

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

A battle between nature and architecture in the Cambodian jungle.

A minotaur, a labyrinth, and a dubious restoration pull in visitors from around the world.

This famous city eluded concrete detection until the early 2000's.

An ancient capital city that dates back 3,000 years old and harbors many surprises.

Surreal riveted sea forts once protected the Kent shores from German attack.

A nuclear bunker built to shelter the politicians and important people of Scotland in case of nuclear attack.

Below a historic English market town lies a secret underground city complete with kitchens, laundries, storerooms, and an underground lake.

Over 4,700 miles of trees being planted to hold back the desert.

A nondescript Seattle restaurant inherited a piece of European history.

This enormous sports car themed amusement park is home to the world’s fastest roller coaster.