In 1329, Christine Carpenter entered this small stone cell in the hopes of becoming a living saint.

Artist Scott Hocking took a dilapidated 1890s barn to create his massive "Barnboat."

Located in the world's highest-altitude Dark Sky Community, this observatory welcomes amateur and professional astronomers alike.

The "World's Largest Underground Business Complex," a 55,000,000-square-foot city underneath Missouri.

One man's dream has turned into this naturally growing chapel made of almost nothing but trees.

The oldest covered railroad bridge still standing in the United States.

This 12-seat movie theater is the smallest in the world.

This groundbreaking 16th-century map is known as "America's birth certificate."

Smallest house in Toronto sits on a lot meant to be just wide enough for cars to drive through.

This short bridge is the only thing connecting a tiny Irish island to the mainland.

Walk down these stairs to get an underwater view of Switzerland's Lake Zug.

The final resting place of the world's first nuclear reactor.

To get to or from this Canadian ghost town, you'll need to cross 11 single-lane bridges.

In 1909, the steepest and most difficult piece of track on the Canadian Pacific Railway was replaced with a series of spiralling tunnels cut into the mountains.

This jagged colossus of a building is mostly held together by an enormous concrete exoskeleton.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

The palace window through which Protestant nobles flung two Catholic regents, thus sparking the Thirty Years' War.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

Watch cheese-flipping robots in action at this factory and museum.

A simple tribute to the microscopic arachnid that gives its juices and its life to help make a speciality German cheese.

A 22-million-year-old sandstone cave is a natural habitat for award-winning cheese.

This unassuming cheese empire in rural Oregon churns out more than 150,000 pounds of cheese each day.

Order cookies baked by cloistered nuns in a 400-year-old monastery.

This medieval cathedral houses stained-glass windows featuring saints and pretzels.