The medieval network of canals hidden underneath the city is opened to explorers each year.

No one is quite sure of the origins of these idyllic natural hot springs at an abandoned mountain resort.

A once-luxurious, now abandoned hotel in the Italian Alps.

Crumbling ruins of the thermal baths that once attracted royals and aristocrats from throughout Europe.

A curious collection of oddities including a lock of Alexander Hamilton's hair and Harry Houdini's ouija board.

The only way to visit this old resort hotel is with scuba gear.

A "gravitational anomaly" located in the redwood forests just outside of Santa Cruz, California.

A monument to the art of slicing people open.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

See massive fossils that are over 200 million years old in northeastern Arizona.

A reproduction of earth's many biomes.

This former stomping grounds of the most eminent astronomers of the early 20th century.

An unrealized dream to wirelessly electrify the entire Earth.

Fossils, railroads, and waterfalls!

One of Canada's oldest museums, the beautiful Redpath has been serving up Natural History and Ethnography since 1882.

This beautifully deceptive waterfall is something far different from what it appears to be.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Site of the first official transatlantic wireless communications.

Home to Hollywood history and a very special salt crystal.

Live long and prosper in Vulcan, Alberta.

World's only nuclear reactor operated by liberal arts undergraduates.

Where the embers of the Big Bang were first detected.

Garden dedicated to native carnivorous plants and site of huge flytrap heist.

The longest burning light bulb in the world.