Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

This rare basalt crater lake is used to study the Moon and Mars.

A dozen U.S. presidents have stayed at the historic resort, which was known as James Buchanan’s “Summer White House” from 1857-1861.

The controversial final resting place of the equally controversial first president of Turkmenistan.

The world's largest bicycle shelter can hold more than 12,500 two-wheelers.

It's hip to be square in Iola, home of the largest town square in the United States.

Next to a newer mosque in Khujand’s main square lies the city’s oldest mosque, whose interiors are spectacularly intricate.

This human-made cave is one of the many snow storage chambers that supported the ice supply industry in the Sierra Mariola area.

The former site of the world's largest paper mill is now a museum preserving the heritage of Canada's pulp and paper industries.

This tiny island protects a number of rare bird species by only allowing visitors to set foot on the beach.

A fantastic reconstruction of a 10th-century Viking longhouse.

Greenland's first shopping mall also hosts the country's government.

1% of Greenland's entire population used to live in this single building, which is now slated for demolition.

This scenic spot is known as the birthplace of Switzerland.

What happens here stays here – unless it affects the whole world.

The fairy tale castle of the "fairy-tale king."

A former top secret nuclear fallout shelter now operates like a hotel stuck in the Cold War.

Canada’s surprisingly controversial monument to Dwight Eisenhower.

This colossal war machine is now a living museum dedicated to underwater warfare.

This foolish Victorian sea fort was converted to a deluxe hotel.

A surprising number of shipwrecks visible just off the Somaliland coast.

German and American troops joined forces to defend this fortress during the strangest battle of World War II.

The birthplace of both the Atomic Age and Godzilla, and the namesake of the bathing suit.

World War II ended before these tunnels built to protect vital oil from Japanese bombs were ever used.