This frequently-photographed waterfall takes only a short hike to visit.

While it is not equipped to peer into outer space this observatory looks like it was built on the moon.

Bridges, terraces, and replicas of historic structures all built of rock and petrified wood by one man.

This lake in the Cascades lives up to its name, disappearing down a hole every spring.

Formerly secret, precariously perched boulders.

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

Europe's largest natural bridge has a 19th century royal chateau built into its side.

This dramatic landscape hidden on the Isle of Skye looks as though you've stepped into the magical realm.

This scale model of our solar system hid in plain sight for years before a physics team sought out all the planets.

An Austrian house of bones filled with hundreds of intricately painted skulls.

The remains of a sunken military ship wreck visible through clear water.

Yugoslavia's biggest underground airport lies in ruins.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

"World machine" built by an untrained Austrian farmer.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

A centuries old castle atop a dormant volcano houses museums devoted to both women and witches.

The shell of a medieval fortress offers commanding views of the area it once protected.

Double spiral staircases are not unheard of, but they are very rare.

Where the lovelorn find a home for their sentimental keepsakes.

The world's most important buildings shrunk to a tiny size.

This house's itty bitty size means no humans allowed.

A miniature train-ride through Slovenia's largest cave system.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

The "dragon babies" of southeastern Europe.