Secret US military film studio in the Hollywood Hills.

These delicate buggers are some of the rarest fossils that have bubbled up from the Tar Pits.

Once strictly off-limits, this lower level housing curious and priceless vehicles of the Petersen Automotive Museum is now open to the public.

World-famous, Pink's still manages to keep its prized cult fetish status.

High on a hill overlooking Los Angeles lives a world famous, high power conical Tesla Coil.

An extraordinary final resting place full of oversized art, amazing statues, and dead celebrities.

Giant Redwood-themed cafeteria operates under the golden rule, "Dine Free Unless Delighted."

Crypt mausoleum in cathedral's basement contains relics of third century Roman martyr, Saint Vibiana.

The legendary building that needed ghostly approval before being built.

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

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

This simple stone memorial remembers a secret, Geneva Convention-defying interrogation base from WWII.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

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

Art deco landmark on the outskirts of Washington, D.C.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

At 207 feet, one of the world's longest continuous escalators.

The "lovely red Vega" of the legendary record-settling pilot.

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

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

Home to items never before seen by the public.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.