For the last century, this international border within a small town has appeared and disappeared various times.

This sign designates the road that leads to the infamous Area 51.

Mysterious meeting place for UFO hunters near Area 51.

In the middle of an extremely unforgiving and desolate high desert is the most secret military facility in the world.

There is one corporation registered for every three square feet of space in this inconspicuous office building.

Remote Honduran Islands with a colorful history.

A lake at the bottom of the ocean.

A striking lighthouse with views of the Gulf of Mexico and of a military air show.

The "worst battleship ever built" is enjoying a grand second act, submerged 30 feet in the Gulf of Mexico.

At low tide, you can see the remains of a 17th-century ship just off a Stockholm island.

This "witch's market" is filled with Amazonian herbs, remedies, and the occasional libido-strengthening tincture.

An old Dutch lightvessel is now stuck in a dock near the mouth of the Suriname River.

This sculpture marks the spot where one of the greatest Roman rulers was proclaimed emperor.

This ordinary-looking mailbox has a rather explosive history.

This portrait of Philip V is always hung upside down, in a protest three centuries in the making.

One of the indelible moments of the American Revolution took place at this location.

This old wooden funicular railway leads to a cemetery in the forest.

Pittsburgh's literal underground railroad.

An abandoned incline railway site is now a green space with six acres of trails connecting hilltop neighborhoods.

Site of an oft forgotten and revolutionary battle.

The last remaining attraction from Paragon Park.

Plans for this peninsula included houses, the United Nations Headquarters, and a nuclear power plant. When none of them worked out, it became an expansive park.

17th-century merchants in Bristol nailed their deals by placing money on these pedestals.

After protestors toppled a statue of a 17th-century slave trader, the pedestal where it once stood remains unoccupied.