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

A tiny park in the middle of some big power politics.

Ancient serpentine sacrifice holder that has stood the test of time.

An Art Nouveau gem hides beneath the layers of city grime obscuring this once-magnificent building.

Taking the subway here means doing so over a bridge located in the middle of an estuary.

A surprising and unconventional mosque hidden in the subsoil of Istanbul.

This museum was invented in a novel before being made real by the author.

This historic hotel preserves many treasures from its heyday hosting passengers on the Orient Express.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

Housed in an old British jail, this spot serves up Georgian, Russian, and Ukrainian specialities with a side of Turkish history.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

One of the newest mosques in a city filled with thousands.

A plaque pays tribute to the artist's longtime London home.

An alleyway plaque is all that remains of the independent Texas' envoy that forgot to pay their rent for over a century.

Claiming to be the oldest hat store in the world, this historic haberdashery had a hand (and a head) in the creation of the Bowler.

Outside of one of Britain's most renowned social clubs, a step installed specifically for the Duke.

A network of bells in the pubs and restaurants around Westminster alerts politicians when it's time to cast their votes.

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

A makeshift shrine to the late rock star is still kept up on the nondescript façade outside 1 Logan Place.

A 1950s beatnik coffee house, turned 60s counterculture hotspot, turned modern music venue.

The Metropolitan Police refurbished the blue box (perhaps not coincidentally) the same year "Doctor Who" returned to TV screens.

An unusual ode to the late Irish playwright, complete with a squiggly bust and coffin-shaped bench.

This museum inside a museum tells the story of London's timepieces.

Charles Babbage's proto-computer, painstakingly brought to life.