An abandoned network of military bunkers and tunnels open for anyone willing to descend into the darkness.

This floating garden in the sky is straight out of a fairy tale, but the real thing is nothing short of magical.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

In the main dining room, a nine-ton boulder caps the fireplace designed by local architect Earl Young.

This complex of vertically-excavated Buddhist, Jain, and Hindu monolithic temples in India's Maharashtra providence illustrates a spirit of tolerance characteristic of ancient India.

Ruins and statues dot the landscape of this tiny island rich with royal history.

Legend has it fairies gathered at the site of this medieval castle.

One of the largest and oldest caravansaries in Persia.

A gardener's enduring labor of love is spread throughout a small Vermont town.

The ruins of a 13th-century monastery that long served as a place of refuge from wars and raids.

A sprawling ancient Jewish cemetery with over 30 rock-hewn burial caves.

The ancient tomb acts as a calendar that keeps perfect time.

The oldest still-inhabited hill fort in India looks like a magnificent golden sandcastle.

The evocative ruins of a 1,000-year-old hill fort lie within a popular tiger reserve.

In the back of a nondescript sports bar is a museum-worthy mural by legendary cartoonists.

The old fire tower is one of the last of its kind in the United States.

This Victorian marvel of engineering and artistic prowess is nicknamed the "Cathedral of Steam."

Its impressive still-working beam engine is a thing of beauty for engineering history fans.

This abandoned Swedish folkpark offers an amazing view over the town of Överkalix.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

This monument remembers the first Japanese Americans forcibly relocated during World War II.

A stoic rock cairn is all that remains to remember one of the more brutal instances of frontier treachery in American history.

An architect transformed this abandoned cement factory into his castle-like workshop.