The first American department store, and home to the largest operating musical instrument in the world.

This elaborate towering structure was once famed for its revolutionary height.

Huge masonic hall in Philadelphia with lavishly themed rooms.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Beneath the southern end of the Golden Gate Bridge is the “Gibraltar of the West Coast,” a fort built to protect the San Francisco Bay from naval attack.

Concrete strongholds stand guard over the Golden Gate.

California's own medieval Italian castle, authentic down to the 300-year-old iron maiden in the dungeon.

A poignant memorial to a young boy whose death spurred a dramatic increase in organ donations in Italy—dubbed the "Nicholas Effect."

Clean, cold drinking water flows from a nondescript pipe in a roadside rock face.

This WWII-era military installation once held an entire city within its walls - now, its walls are falling down.

A farm in New Jersey grew a most unusual crop for AT&T's testing purposes.

A gift from Japan, 17th-century lantern stands among the cherry trees at D.C.'s Tidal Basin.

The tunnel under the Capitol Building where Congress takes out its trash.

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

The National Park Service’s best-kept secret with views that rival any in D.C.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

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

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

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

The walls of the iconic dome are hollow and have a secret stairway.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

Stalinist skyscraper built with help of cryotechnology.

One of the world's tallest statues is also one of its most hated.