After it was swallowed by a Georgian mansion, this medieval castle remained forgotten for centuries.

Packed with gear and memorabilia, this museum chronicles the history of skiing and how its rise shaped New England.

This extraordinary Depression-era expenditure was modeled after a postcard of a Mediterranean hotel.

Dublin's most modern, visually spectacular bridge is modeled after Ireland's national emblem.

The home of the first American-born saint is one of the only curved buildings in New York.

The ancient tomb acts as a calendar that keeps perfect time.

A tour de force of a fountain, memorializing a man who loved fountains more than anything else.

One of New Jersey's oldest surviving buildings still bears the mark of our former British overlords.

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

Every equinox this Maya pyramid puts on a spooky ancient light show.

Part of a WWII submarine is lurking outside the Washington Navy Yard parking lot.

Before Nixon, "watergate" meant canals.

The national park was once a plantation estate.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

As the Dead Sea continues to deplete, massive sinkholes open along its banks.

This spiny beast guards an artist's village while vying for the title of largest lobster in the world.

The Pentagon is so large that it was planned like a city, complete with internal highway infrastructure.

This unique historical monument features large concrete spheres designed to resemble fallen stars.

A Memphis park where you can walk the whole Mississippi River in one go.

Yo, Adrian!

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

With nickel-steel armor and three-inch thick bullet resistant windows, FDR's train was a rolling fortress.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.