Gothic tower mentioned in Thomas Hardy poem "The Channel Firing."

This abandoned gun tower was built to defend the River Thames from a French naval attack.

The elegant structure of this 19th century railroad bridge creates an illusion of infinity.

This historic abandoned train station looks like a stop for ghost trains.

This foolish Victorian sea fort was converted to a deluxe hotel.

Taxidermied animals galore, by appointment only.

This mysterious underground cave in Shropshire dates back to the 18th or 19th century.

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

A network of concealed passageways lies within a busy London Underground station.

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

A former seaside jewel built for the everyman is now simply a neglected art deco fortress.

Historic Greenpoint theater, turned roller disco, now housing a chain pharmacy store.

This Queens hospital has stood abandoned for almost 20 years after its patients were secretly relocated in the dead of night.

One of only two remaining Victorian-era greenhouses in New York.

Hidden in one of New York's oldest subway stations is the final remnant of the site of the bizarre Shakespeare Riots.

An unassuming secret door once led to a legendary watering hole.

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

A tunnel once abandoned now thrives with graffiti art as an off-limits makeshift gallery.

A dilapidated dock tells the story of Titanic's missed arrival.

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

Two planes stand abandoned after the closure of an aircraft-themed restaurant.

This is what trains will look like after the zombie apocalypse.

The now-abandoned Fascist summer colony served a dark purpose during World War II.