This Roman underground canal was the longest tunnel ever built until the late 19th-century.

Across this single-file rope bridge is what has been claimed to be the edge of continental Asia.

One of Indonesia's tallest, this waterfall takes a 390-foot plunge into the Lake Toba caldera.

Rare wooden escalators lead deep down into an otherwise staggeringly monotonous tiled tunnel.

This breathtaking island on Rwanda’s Lake Kivu is a haven for thousands of fruit bats.

These unique stepping stones hug a river's edge to take hikers on a journey through a limestone gorge.

This giant weaving shuttle celebrates Lancashire's importance during the Industrial Revolution.

The remains of a historic plantation nestled in between a parking lot and the rental car return at Reagan National Airport.

This historic mansion was built as a symbol of love between a husband and wife.

This little brick tunnel built by Confederate forces was used to conduct surprise attacks on the railroad.

This ducal residence was once home to a future Russian empress and a French king in exile.

At Ramahyuck, the Gunaikurnai people were forced to trade their freedom and culture for protection. Today, a cemetery is all that remains of the site.

Once the legendary capital of the Dacian Kingdom, this city has been reduced to mere ruins.

This ruined fort and statue are a testament to the last king of Kaua‘i’s savvy diplomacy skills, which briefly brought Russians to Hawai‘i.

These trenches were used to train the Scottish military for life on the frontlines of World War I.

Sleep where gangsters fell amidst smoke and flame, with nary a bullethole to show for the legendary struggle.

One of the largest private collections of cars manufactured by the short-lived Franklin Automobile Company.

Designed as a labyrinth, this subterranean prison was crafted without bars or doors.

This historic stone barn is the former home of legendary cattleman Charles “Lonesome Dove” Goodnight.

This crystal clear water basin feeds the Lao river and powers a hydroelectric power plant.

An entire shopping mall and industrial terrain named for the time the king of Sweden's car went into a ditch.

Civil War-era Fort designed to withstand invasion and attack, with tricky traps called "murder holes."

The last remaining attraction from Paragon Park.

An extensive collection of ancient Egyptian artifacts and mummies.