A Portuguese Jewish cemetery filled with stunning grave monuments that date back to 1614.

This massive mural by famed pop-artist Keith Haring was hidden for almost 30 years until its 2018 rediscovery.

Famed for its pie, this eatery has a hidden tunnel that allowed Catholics to secretly walk to church during the Reformation.

Seven mini rowhouses fill the gap between 54 and 70 Westerstraat.

Some 80,000 Delft Blue tiles line the inside of this Amsterdam walkway.

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

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

This mural painted by Keith Haring was done without payment as a gift to entertain the children at the Hôpital Necker.

This demon atop the Notre-Dame de Paris looks utterly bored.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

The video game-themed street art first popped up in the French city.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

The narrowest street in Paris.

A surrealist timepiece by the artist of melting clocks.

Built by prisoners of war, the largest small-scale model ever built includes eight miles of tiny streams that now sit abandoned.

The last intact steam engine factory in the United States.

A decaying building marks the site associated with Emmett Till's brutal 1955 murder, which helped sparking the civil rights movement.

This roadside attraction in the woods of Mississippi is a scalable replica of the Holy Lands during biblical times.

In the mid-20th century, a tamale-slinging juke joint attracted a diverse clientele in the Mississippi Delta.

A preserved stretch of ancient fossilized trees with an impressive gem collection to boot.