Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

A breathtaking viewing platform over the Alps.

The topiary maze at the Habsburg hunting lodge.

The fairy tale castle of the "fairy-tale king."

Daily jousts and dancing barrel makers in Munich's mechanical clock.

A surprising collection of bronze faces beneath a bridge in Loveland.

Air Force Academy Chapel made of 100 identical tetrahedrons works to inspire those of all religions.

These decaying bridges 1,000 feet high are a reminder of the skill it took to cross the Colorado Rockies by rail.

When ecosystems collide in the arid Southwest.

Paranormal experiences in this hotel's room 217 led Stephen King to write "The Shining."

This huge dam across the Colorado River caused an armed standoff between two U.S. states.

A monument to the one-armed geologist who led the first documented expeditions through the Grand Canyon.

A geological mystery on Camelback Mountain.

This collection of Wild West movie memorabilia also claims to hold some secrets of the Lost Dutchman's mine.

This 40-room dwelling tucked within a cliff was built by the basin's prehistoric residents.

The largest natural travertine bridge in the world is nestled in a small canyon in central Arizona.

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

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

A sculpture made of 10 Cadillacs as a monument to the "Golden Age" of the American automobile.

The Pentagon sits on a former island that was in Virginia at low tide and D.C. at high tide.

The final resting place of an unidentified revolutionary soldier sits behind a Virginia church.