It's believed that this small church was connected to the Hagia Sophia via a secret tunnel.

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

Turkish adventurer antiques in the heart of the Grand Bazaar.

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

A fountain standing as a testament to a doomed alliance.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

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

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

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

The world’s second-largest flood defense barrier has protected London for decades.

This Finnish town on the Arctic Circle is trademarked as the Official Hometown of Santa Claus.

A grand Wetherspoon pub set in a former opera house dating back to 1902.

Time has been frozen at this station since the bombing in 1980—or so it was believed.

This 2,000-year-old Doric bridge is still open to pedestrian traffic to this day.

This monumental neo-Renaissance tomb in Vyšehrad Cemetery is the final resting place for Czech cultural legends.

The oldest floral clock in the world still functions today.

These markers note British stars of both stage and screen.

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

The rose garden in Regent's Park where Pongo and Perdita met for the first time in Disney's "101 Dalmatians."

A commemorative plaque at the door pays tribute to an "American Patriot" known for his betrayal.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

This tribute to the fictional detective stands at the famous literary character's address.

This London marker celebrates the spot where the world-famous English band was founded.

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