Step into a cartoon at this Seoul café that aims to evoke a two-dimensional scene.

This stunning natural double arch, the largest in the Alps, went undiscovered until 2005.

Medieval irrigation channels built into the sides of mountains provided Valais with water for hundreds of years.

Filled with goldfish swimming in a shallow pool of sea water, this ancient crypt is more wishing well than burial site.

A marvel of Byzantine engineering under the streets of Istanbul.

A modest stone circle in North Wales.

A submerged archeological park still holds the wonders of a Roman Sodom.

As can be expected from a centuries old church built in a canal city, the undercroft of this house of worship is beautifully flooded.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

Once an indicator of social class, the color blue has come to define this city on the edge of the Thar Desert.

This beautiful system of tunnels built into natural rock serves as a centuries old plumbing system.

An underground city of salt.

This massive underground salt mine now holds a sci-fi theme park in its depths.

These tombs were built into the side of a mountain so that ancient angels could reach the dead.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

While most books are made of wood, these wooden books are truly made of, and all about wood.

These faux-cliff dwellings allow visitors to climb around on a replica archaeological site.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

The secret city built by the Manhattan Project.

The world's first time capsule lies behind a welded steel door in Atlanta.

The ruins of a cotton mill that was burned in the Civil War are still hidden in a Georgia forest.

This structure among the trees was the result of divine inspiration.

The remains of one of America's first radiation testing grounds still rest ominously in a Georgia forest.

These ancient ritual mounds are our best window into the culture of the ancient Mississippians.