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

A nondescript building that's been functioning as a speakeasy for nearly a century and a half.

A pair of slides and a tree-lined stair corridor have been an urban oasis for nearly 40 years.

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

There is no trying to fall in love with this Star Wars fountain, you just do or do not.

A 140-year-old castle with underground caves hidden in San Francisco.

A hidden path at the National Theatre lets you look behind the scenes of the latest productions.

Behind one of the world's most impenetrable vaults is a massive collection of retail silver.

"Purveyors of traditional sweets and vintage treats."

A high-end clothing boutique with a curious basement art installation.

The commemorative stone column conceals a secret laboratory.

The 2,000-year-old beam is tucked within the pedestrian entrance to the old London Bridge.

William Smith's iconic "map that changed the world" is hidden behind a curtain in the Geological Society building.

An architectural oddity hides in plain sight on this iconic London bridge.

This unique bridge curls up like a caterpillar to let boats pass and then unfurls again to span a small canal.

A bronze bust commemorates the heroism of the secret agents who led covert operations against the Nazis.

"We gonna rock down to Electric Avenue, and then we'll take it higher..."

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

There's an exclusive Beefeaters pub hidden in the Tower of London.

This secluded walkway overlooks a magnificently wild London green space.

The fierce beast perches atop a pedestal marking where the historic City of London gates once stood.

It is still illegal to "quarrel" at this unlikely urban oasis built on top of an electrical substation.

This overlooked street light once served as a KGB dead letter box.

A statue of the legendary Celtic warrior queen who fought the Roman invaders stands in one of the cities she once destroyed.