Proof of ancient aliens, or simply a creative way for farm laborers to clear their fields?

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

The final resting place of the great escape artist, where some still gather to wait for his escape from death.

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

A Stockholm metro station is home to an escalator that is not only the longest in Sweden, but among the longest in the world.

The Swedish flag over this small naval fort signals that the nation is at peace.

This small museum nestled inside a souvenir shop is dedicated to Sweden's most well-known toy.

Stockholm's tiniest statue is of a small boy looking at the Moon.

The discovery of an old wall led to the creation of this fascinating museum about the city in the Middle Ages.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

Sweden's "good old days" painstakingly re-created in a model village.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

At the base of the Golden Gate Bridge, a small sign basically begs for a high-five.

Once the largest windmill outside of Holland, with enormous 114 foot sails.

The key to turning shifting dunes into the green oasis of Golden Gate Park.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

San Francisco's urban bison herd has persisted in the face of extinction, development, and disease.

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

Staircase winds down the side of Telegraph Hill through gardens, wild parrots flying overhead.

There are lots of hands and feet stamped in the cement in front of Grauman’s Chinese Theater, but Mel left behind something extra.

Scores of vintage street lamps shine along L.A.’s Miracle Mile.

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

Hollywood's most famous landmark, the "temporary" sign that has stood for decades longer than intended.

These four islands right offshore have waterfalls, colorful lights, fancy buildings, and a secret purpose.