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

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.

This groundbreaking 16th-century map is known as "America's birth certificate."

One of the three perfect vellum copies of this historic book known to exist is on display in a specially-designed case.

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

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

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

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

This statue of one of baseball’s greatest pitchers looks like something out of a sci-fi horror movie.

Lady Liberty's first beacon of enlightenment is now displayed in a museum near the statue.

A popular European tradition makes its way to the states on one of America's most famous bridges.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

Elevated freight railway turned wildly successful urban park.

A crumbling hospital from the 1850s on Roosevelt Island.

Once thought to be the fabled Holy Grail, it is now known to be an oil lamp.

The oldest family-run luncheonette in New York, last renovated in 1948, still serves food and drinks the old-fashioned way.

One of only two commuter aerial tramways in the United States.

The cutest shrine in Kyoto is dedicated to bunnies.

Burial mound for the ears and noses of thousands of mutilated Korean soldiers.

A beautiful bamboo trail tucked in this famous Japanese Shrine.

Twelve hundred stone carvings guard this off-the-beaten-path Buddhist temple.