Portland had a unique approach to Cold War-era protections.

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

This forgotten boat elevator was an engineering marvel in its heyday.

The ruins of Scottish sea salt production.

This majestic tree has survived 400 years of storms, droughts, and floods, and is a beloved natural landmark in Missouri.

Originally planted by the ancient Carthaginians, this sprawling palm grove is one of the largest in the world.

A breathtaking flower tunnel bursts with beautiful golden blossoms.

This grand old 80-foot sequoia towers above the buildings in the city’s retail center.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

Traditional Appalachian dances such as the Georgia Rang Tang and the Shoo-Fly Swing are kept alive at this weekly event.

The highest point in North Carolina and the United States east of the Mississippi River, Mount Mitchell is named after argumentative explorer Elisha Mitchell.

These eerie outliers of the lightning bug family glow a mysterious blue color.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

The final resting place of the camel who served with the Confederate Army during the Civil War.

A plaque marks the underground site of one of London's "lost rivers."

One of the last free public hot springs is decorated with hippie art.

No one is quite sure of the origins of these idyllic natural hot springs at an abandoned mountain resort.

This remote British Imperial telegraph relay outpost drove men insane.

This ruined fortress was the stronghold for a persecuted medieval leader and his infamous Assassins.

The medieval town's star-shaped walls are geometrically dazzling, though not entirely impenetrable.

A 120-year-old legend concerning an empty circular patch in the North Carolina woods.

A long-disputed island that Denmark and Canada claim by periodically alternating flags and bottles of liquor.

Mysterious ancient boulder carved with petroglyphs in the mountains of Western North Carolina.