The 28,000-year-old specimen is remarkably intact.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

An overlooked memorial honoring the local Washington residents who died in World War I.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

A historic ruin just 20 feet away from a busy highway onramp.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

Take a dip in the world's largest mineral hot springs pool.

These markers are used to document elevation changes around the famed dam.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

Perhaps the most scandalous statue of America's first president.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

The United States Capitol's former columns still stand.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

Two rocks in a perpetual kiss and one of "the most romantic spot in America."

Dozens of rockets and missiles are on display outside a testing facility in the Utah desert.

One of the most elaborate displays of Jellyfish is on display at the aquarium.

Pyramid home to an obscure religious group that practices modern mummification.

This church on a Tohono O'Odham reservation has stood since 1797.

After the oysters have been shucked, and the restaurant's been shuttered, the terrazzo sidewalk from the 1940s is all that remains.

Inside this striking glass building, visitors can see thousands of dinosaur fossils in the positions that nature deposited them more than 150 million years ago.

A gift from Scotland to the United States in memory of the 270 lives lost when Pan Am Flight 103 exploded over Lockerbie due to a terrorist bombing.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.