The attic of a four-century-old canal house hides a clandestine church.

Cat art as far as the eye can see.

Amsterdam's former hotspot for public executions and dissections.

A hidden church in a hidden courtyard tells the story of the Miracle of Amsterdam.

In the days before house numbers, these colorful signs held clues about various buildings' purposes.

This monumental work of art symbolizes the coming together of a previously divided city.

Cold war icon and onetime "hole" in the iron curtain.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

These former Nazi anti-aircraft towers offer a singular view of the north of Berlin in the summer, and a sanctuary for bats in winter.

A line number in Amsterdam that will likely never be used again due to its tragic history.

This historic Amsterdam bar used to accept sailor's monkeys as payment.

Thousands of pieces of art have been carved into the rock at the site of an ancient volcanic eruption.

This opulent Pueblo Deco movie palace melds Art Deco and Native American motifs.

This giant pocket watch is the third iteration of a local landmark that has been standing just off the Santa Fe Plaza for over 100 years.

The oldest continuously occupied public building in the United States.

More than a century after her death, Little Gracie Watson remains one of Savannah's most often-visited residents.

Performers, intricate sets, and a real speakeasy tell the story of the 18th Amendment.

One of Savannah's oldest and most haunted cemeteries, featuring graves desecrated by Sherman's Union Army.

One of the oldest family businesses in Reykjavík serves lamb-based hot dogs.

A monument dedicated to the civil uprisings that took place during the Pots and Pans Revolution.

This bridge over D.C.'s Rock Creek Park is sometimes called the "Buffalo Bridge" because of its four buffalo sculptures, which were cast from a single piece of bronze.

This historic boathouse was constructed using salvaged lumber from burned barns.

Washington D.C.'s most famous pianist, composer, and bandleader still tickles the ivories outside Howard Theater.

Outside the Department of Transportation, a collection of artifacts honors the history of how we get around.