Edison's cast-in-place concrete houses were a failure, but way ahead of their time.

Ancient structures used to make and preserve ice in the deserts of Persia.

For decades, it has disappeared and reappeared as water levels rise and fall.

An obelisk marks the farmhouse where the founder of Mormonism was born.

This natural wonderland is a unique chance to explore a Carolina bay, a mysterious geological formation of unknown origin.

These pools have been abandoned for over 20 years.

A star-shaped fortress town fort built in the geometric model of the Renaissance utopian city.

A slab of sandstone covered with mysterious 1,000-year-old rock carvings from a vanished North American culture.

Rare recess caves fill this unbelievably beautiful Ohio park.

The quiet canyon has a tumultuous history involving a doomsday cult.

Cemetery featuring rare glass-fronted columbarium.

Chicago's North Park Village was once the largest municipal sanatorium in the country.

Mysterious Incan ruins on a tiny island in Lake Titicaca.

The singular ruins of a mysterious lost city.

This ancient altar emerges from the thick forests to reveal the mysteries of Etruscan sacrificial rituals.

Coast along one of Japan’s mountain railways for coveted views of magnificent hydrangeas.

The mysterious megaliths have enchanted and intrigued visitors for thousands of years.

A fantastical 13th-century fortification sandwiched by a modern hotel in central Brussels.

The ruins of an ancient temple to the Aztec wind god discovered in the middle of a metro station.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

This fantastic cave remained unexplored until 1948 when three schoolboys discovered a hidden entrance.

An abandoned 14th-century castle and prison complex on a small island in the Neva River.

This Roman amphitheater is said to be King Arthur's legendary Round Table.

Odd outsider art installations surround a Gold Rush-era ghost town.