Astronomical observatory above Lake Titicaca.

A valley of unique erosion patterns lends to a view like nothing on Earth.

A striking 12th-century-style castle built on the edge of a cliff.

The only surviving prototype for Buckminster Fuller's house of the future.

These ruins of a pre-Columbian cliff village are among the most beautiful and well preserved in New Mexico.

A Victorian cemetery in the heart of Brooklyn remains a popular mecca of morbid curiosity.

A preposterously luxurious hotel with gold-plated iPads, Rolls Royce chauffeurs, and a staff that trains by watching "Downton Abbey."

A forlorn fishing village on the coast of Labrador, full of shipwrecks and Spanish gold.

A lake in the middle of the tundra of Quebec is said to be the purest freshwater lake on Earth.

A treasure trove of astronomical, mathematical, and scientific instruments at Cambridge University.

A sign at the end of the Santa Monica Pier marks the traditional end of the legendary American highway.

Steepest flood safety railway in the entire world.

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

The largest university building in the West is a gothic masterpiece containing dozens of theme rooms based on different countries.

Board a mine car and descend the #190 slope 300 feet underground into the Clark Vein of coal.

An indoor miniature village and labor of love for Laurence Geiringer, a model railroad enthusiast.

"Dark Sky Park" is heaven on Earth for astronomers, one of the rare U.S. locations with no artificial light pollution.

Where the oil industry began.

On the outskirts of a desert trading village high on the Andean plain, steel giants have been destroyed by salt winds.

Revolutionary War casualties fill the only 17th century structure remaining in Manhattan.

The boulder on which Alexander Hamilton laid his head as he died can still be visited on the New Jersey coast.

This small New York museum examines Chinese history from its origins right up to its arrival in the city.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.