A strange machine made to evaluate the world economy using water and lots of tubes.

The seamy, underground secrets of Portland's criminal past.

Walk through living pictures and music in the Cathedral of Images.

Amazing and mysterious Neolithic settlement on Scotland's Orkney Islands.

A walk through the historic city center, under the streets of Seattle.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Giftshop catering to cryptozoologists and anyone with a sense of humor.

Giant acorn-shaped 19th century gazebo from which suburban Washingtonians gazed upon the original "silver" spring.

Tiny observatory made big contributions to the study of the Earth's motion.

Bizarre Cavern.

A nightmare for the claustrophobic lies hidden in Southeast Asia.

An enormous concrete structure built over a nuclear crater.

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

The world's largest drain sits below the city of Kasukabe, Japan.

WWII rocket launchpad in rural Germany and site of operation backfire.

The remnants of an early American attempt at missile defense.

The kind of mixed-up place that drives archaeologists crazy.

A mysterious air force base built to resemble a Long Island fishing village.

Abandoned city hidden from the world by tropical forest and isolation on the coast of Kenya.

A Belgian self-built tower inspired by the Bible and ancient civilizations.

Keshwa chaca, among the last handwoven Incan bridges, crosses Apurimac Canyon in Peru.

Experience a charming 1930's version of "infotainment."

The ghost town that ended up on Ebay.

Walk through the actual strap iron cells and solitary chambers of Arizona Territory’s first prison.