Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

The world's longest known cave system.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Forget Hollywood, one of the biggest stars in the world can be found in Roanoke, Virginia.

The only known Futuro house in North Carolina sits along a stretch of desolate highway on the Outer Banks.  .

This shifting North Carolina sand dune is an odd little desert surrounded by oceanic forest life.

The maritime museum that boasts the largest nautical library in the western hemisphere.

The final resting place of two (or three) presidents, one vampire, and 18,000 Confederate soldiers.

Exact replica of the ancient monument, but much, much lighter.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

There’s a hidden military meme engraved on the World War II Memorial.

Look closely and you’ll notice that the color changes a third of the way up the tower.

A local prank turned town icon.

Frank Lloyd Wright’s most iconic home dangles over a Pennsylvania waterfall.

The house that Frank Lloyd Wright "(shook) out of his sleeve at will" at the age of 86.

There aren't too many operational funiculars around, but Pittsburgh has two!

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

Ruins of a once-prized railroad station in New York.