An artsy hidden staircase leads to breathtaking views of San Francisco.

World's largest collection of serial killer artwork and other macabre exhibits.

The taxidermied remains of Charles Dickens' pet raven, which helped inspire one of Edgar Allan Poe's most famous poems.

The origin of this mechanical boy was a mystery until he revealed his maker by writing it in perfect cursive.

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

The first bell ever cast in Boston was cast by Paul Revere...and sounded terrible.

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

This curved Manhattan building was built to house the opulence of John D. Rockefeller's oil empire.

Unrepaired walls from a 1920 anarchist bomb attack.

Four hundred granite steps were built into this massive rock by the National Park Service.

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

These millipedes glow not out of attraction, but as a not-too-subtle warning.

The world's longest outdoor covered escalator system transports commuters through Hong Kong's hilly terrain.

Faceless white figures loom over the city from the rooftop.

This cemetery served as the only official burial grounds in Cambridge for nearly 200 years.

Two plaques commemorate the site of Shakespeare's first theatre.

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

One of the indelible moments of the American Revolution took place at this location.

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

I Street Bridge is the heaviest swinging center bridge in the United States.

A shape-shifting buy-sell-trade bookstore, born to Beatnik Era spirit.

The inspiration for H.P. Lovecraft's horror stories and Batman's Arkham Asylum is now a condominium complex.

A remote crossroads honoring a fallen talent.

The miraculous hydrant that saved the Mission District in 1906.