An inconspicuous footbridge beloved by San Diego locals.

The famed architect designed this Minnesota gas station of the future with a lookout tower.

This fancifully decorated Victorian home in New York’s Hudson Valley is the only known fully domed octagonal residence in the United States.

Possibly the most beautiful carillon in the world, set atop Iron Mountain in Florida.

This tiny little island has, as the name says, just enough room for its single house.

A mysterious monument meant to be a guide into "an Age of Reason" was destroyed after an apparent bombing.

In the foothills of the lesser Caucasus, a centuries-old fortress still stands.

A creek tumbles over a series of step-like rocks to create this scenic water feature.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

The Arctic Archipelago is home to world's largest third order island: an island in a lake on an island in a lake on an island.

The deepest hole drilled in the name of science, where evidence of Precambrian life was found.

This precariously perched fortress was once ruled by a crow-worshipping baron.

This medieval hilltop village was abandoned at the end of the 19th century, after existing for more than 500 years.

This 170-year-old Swiss guesthouse built into the side of a mountain is best accessed by a cable car.

The ruins of a medieval castle that once belonged to one of the most powerful families in the Netherlands.

Legends of treasure and spirits flow from this this fairy tale-like oasis.

This amazing ancient cave was kept secret for seven years to protect it from the public.

The Greek War of Independence was declared at this medieval Byzantine sanctuary.

This castle has links to Portugal’s founding and struggles for independence.

This unique wooden mosque resembling a Chinese pagoda was said to be built without the use of nails.

An Aztec temple, the largest man-made pyramid in the world, sits buried in earth with a Spanish church set on top.

Eco-village hidden in the foothills of the Alps that created a massive system of psychedelic underground temples.

The world's longest outdoor escalator takes visitors to the top of China's largest dam and is also shaped like a dragon.

Granny Smiths and Fujis can both be traced back to Kazakhstan, where apples still grow wild.