This historic Boston building has gone from personal estate to porn theater and back again.

The oldest working bell set in North America, the bells at Old North Church sat silent for their first four years in Massachusetts.

On a former island, this old fortification once used to protect the Boston Area and started Edgar Allan Poe in his military career.

This massive tea kettle was once a promotional stunt for the Oriental Teashop.

Painstakingly built dioramas sit unnoticed in a Boston office building.

The site of Paul Revere's historic two lantern warning.

Ralph Waldo Emerson spent two years living here decades before it became a Frederick Law Olmsted-designed park.

One of the oldest used bookstores in the U.S. has been selling antiquarian treasures since 1825.

Dim sum, served in a grand old theater.

The oldest Italian café in Boston, this spot also serves as a veritable museum of vintage coffee ephemera.

Tombstones and enigmatic inscriptions hide within a vault beneath a popular London arts venue.

Buried for centuries, this hidden cellar is all that remains of London's medieval Whitefriars Monastery.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

A crumbling hospital from the 1850s on Roosevelt Island.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

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

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

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

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

The quaint little store that is said to have inspired a famous Dickens novel was only given its name after the book was released.

Open since 1938, this diner has kept its fountain, malt machine, and all the gum that greasers left beneath its counter.

A sixth-century Byzantine cistern hidden below a modern carpet store.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.