The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

This Wall Street bar was once a hub of revolutionary activity where Washington famously bid farewell to his troops.

The original toys that inspired the beloved children's stories are on display at the New York Public Library.

The highest bridge in America was built for an almost unnervingly small amount of money.

Hundreds of glow-in-the-dark objects light up a museum in a historic zinc mine.

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

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

Once the tallest building in the world and the site of "the highest dinner ever held in New York" this building now holds the most expensive penthouse in the city.

Ride the subways of yesteryear.

Tucked away amidst some of the most famous addresses in the world is New York's only fraction of a street.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

A mysterious castle built as a monument to lost love.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

Mysterious 500-year-old tapestries depict a unicorn hunt.

A celebration of capitalism in Midtown.

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

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

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

The world's longest known cave system.

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

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

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.