19th century cemetery hidden in Brooklyn's Prospect Park.

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

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

A crumbling hospital from the 1850s on Roosevelt Island.

Only a few pieces remain of the structure that carried people and goods across the Thames for some 600 years.

This life-size monument honors the legacy of a famous literary feline.

This striking statue brings a scene from the African savannah into central London.

The final resting place of a German diplomat's beloved companion.

The ruins of a church destroyed by both the Great Fire of London and the Blitz, now turned into a peaceful garden.

The medieval woodcut-style artwork chronicles life in medieval London.

A statue of the original Pearly King is hidden in a church's crypt.

Hidden in the courtyard of the Victoria and Albert Museum is a little-known tribute to two celebrity pooches.

A tribute to the intrepid explorer and his crew who perished in terrible conditions on an ill-fated expedition to the Arctic.

These Victorian era devil sculptures were designed to spite a local vicar.

It celebrates a very stinky task and salutes London's fatberg-vanquishing team.

Legend has it that seven Anglo-Saxon kings were coronated on this stone, located in the appropriately-named town of Kingston.

A plaque marks the underground site of one of London's "lost rivers."

Victorian-era Londoners really wanted to believe this 17th-century cistern was actually an ancient artifact.

This peeling mural of Adam and Eve was inspired by the greenhouses at Kew Gardens.

It's a mystery why these remains were found with no traces of their bodies in sight.

The Art Deco artwork depicts gilded carriers of deadly illnesses.

A portly statue of a golden boy commemorates an unusual cause of the Great Fire of London: the sin of gluttony.

The plunge pool is a surviving relic of a rowdy royal residence.

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