The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

Quite simply the largest tree in the world (by volume).

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

A monument to the one-armed geologist who led the first documented expeditions through the Grand Canyon.

These elusive, isolated rodents evolved into a distinct, locally iconic subspecies.

A geological mystery on Camelback Mountain.

The unusual burial monument of Arizona's first governor.

Once a year, at exactly 11:11 a.m., this monument comes to life.

Come for the pizza, stay for a performance on the world's largest theater pipe organ.

An homage to everyone's favorite prehistoric cartoon family.

The world's largest military aircraft cemetery.

These free-roaming horses were once destined to disappear from the land.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

These unusual rooms on wheels are holdovers from the 1960s.

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

The controversial urban planner who designed Washington, D.C., was buried in Maryland, and can presently be found in Virginia.

The romance of early commercial flight still fills this Art Deco destination.

Please don’t anchor your boat onto the Department of Defense’s underwater data cables.

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

The remains of a historic plantation nestled in between a parking lot and the rental car return at Reagan National Airport.

The FBI's urban training course may have the highest fake crime rate in the world.

The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.

FDR's Art Deco hospital tower was hopelessly inefficient.