A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

A quiet memorial to those who died saving others in the heart of the City of London.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

On a wall in linear London, a plaque hangs at the high water mark of one of the worst floods in fictional Kcymaerxthaereal times.

A little sculpture with a large wardrobe.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

A collection of objects supposedly singed by the hands of souls in purgatory.

Architectural monsters are devouring this palace's every door and window.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

New York City's smallest piece of private property.

Phil Mortillaro uses keys to bring art back to the Village.

Tucked away amidst some of the most famous addresses in the world is New York's only fraction of a street.

A Manhattan office building is home to the world's largest chess board.

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

Twice a day one of these tragic bronze mariners drowns with the tide to remember all those the sea has taken.

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

Manhattan's lighthouse, erected at the insistence of the unsinkable Molly Brown.

Detailed facade of a brownstone in Boerum Hill.

Try not to get slimed in Tribeca.

Blighted Irish field and the ruins of a 19th-century cottage on the edge of urban Manhattan.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.