The 7,000-year-old calcium carbonate formation creates a magnificent natural bridge.

This Nebraska town wants to double its population with plywood cut-outs of townsfolk.

An experimental, automotive replica of Stonehenge.

A precariously balanced rock perches on the edge of a cliff created tens of thousands of years ago by glacial erosion.

This popular pilgrimage site offers a hole filled with holy healing dirt.

These aggressively sustainable art homes look like something out of 1970's science fiction.

This geothermal hot spring hides beneath a slowly growing mineral dome.

An earthwork sculpture built by Robert Smithson in the Great Salt Lake only reemerges during drought.

The Hopi-style structure was built by the man who discovered Desert Hot Springs' famous mineral water.

Puffin enthusiasts flock to Europe's largest seabird cliff, which over one million birds call home.

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

Abandoned bull fighting ring, slowly falling apart in Uruguay.

Within the former ghost town of Cisco is a carefully restored tiny town with one resident and its own art residency.

A sprawling collection of over 106,000 toys from around the world.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

These elusive, isolated rodents evolved into a distinct, locally iconic subspecies.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

An urban laboratory.

Limestone caves with spectacular showcase chambers.

A spiritual vortex among the red rocks in Sedona.

On the outskirts of a reborn ghost town, a decaying post office remembers the bad old days.

America's only nuclear missile silo open to the public.

A reproduction of earth's many biomes.

This mining town boomed in the Atomic Age when uranium was gold, only to be abandoned when the industry collapsed.