Hundreds of antique bank vault locks on display in New York City.

The "Prussian Versailles" that is as glorious today as when it was built.

Avoid gangster interaction while window-shopping.

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

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

Sniff the Titan Arum's rotting flesh.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

The site of the climactic scene from the classic horror film is now a historic landmark.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

At 207 feet, one of the world's longest continuous escalators.

America's post-nuclear-attack chambers of Congress.

Ruins of a Carnegie family mansion on Cumberland Island.

This peaceful Massachusetts graveyard was one of the first "garden-style" cemeteries in America.

A hidden "place of interment for gentlemen."

This exemplar of modernist architecture is meant to captivate and inspire students of the Cooper Union.

An artist's cute bronze subway sculptures belie his violent artistic past.

The most confusing clock in New York.

Elevated freight railway turned wildly successful urban park.

A crumbling hospital from the 1850s on Roosevelt Island.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

A former insane asylum despised by Nelly Bly and Charles Dickens is now fashionable apartments.

A little lighthouse in New York City, surrounded by mysterious stories of insanity-driven construction.

This immaculate and historic water garden culminates in a massive stone dining table with an inset fountain for chilling the wine of the Cardinal's guests.

A 16th-century horror show built in a lovely Italian garden.