The atomic museum in the basement of this German castle displays long strands of replica uranium cubes.

The narrowest street in the world is in danger of closing up entirely.

A New York–based physician returned home to Spain to build his own elaborate monument to Christopher Columbus.

One of the most well-known city festivals in the world.

This bomb was once used as a church after it failed to detonate.

This natural hill rose another 130 feet from the debris and rubble added after World War II.

This old wooden funicular railway leads to a cemetery in the forest.

Remnants of a cone-shaped Nazi bomb shelter.

A tiny, intricate model railway system.

Home of the largest single-phase AC generator in the world.

This outdoor library provides around-the-clock access to around 7,000 books.

The residents of the Neighborhood of Make-Believe live without much fanfare within the Pittsburgh Children's Museum.

The universally beloved children's television figure is interred on a high hilltop in one of western Pennsylvania's oldest cemeteries.

This narrow fjord-like bay is the largest ria in the Mediterranean Sea.

A World War II evacuation tunnel turned into a history display of Croatian state and people.

This unique structure allowed boats to bypass underwater mine barriers in the channel to enter the harbor.

Inside this small chapel tucked away in the forest is one of the most well-preserved Danse Macabre frescos.

This 135-year-old weather station studied the effects of the climate on human health.

Colorful concentric circles honor a small Croatian town's supposed spot at the nucleus of it all.

Just a few miles from Novalja, a strange geological oddity has left scientists baffled.

This heart-shaped island looks substantially less lovely after a recent bulldozing project.

This military tunnel dates back to World War II and provides visitors with a little wartime adrenaline.

The Renaissance-era courthouse is a relic from the fortified town's centuries of Venetian rule.

Built as an anti-fascist tribute, this surreal Yugoslav memorial became an unwelcome symbol after the Croatian war for independence.