This massive subterranean fissure is known as the "underground Grand Canyon."

This one-time health resort was used by aristocrats around the world.

A whimsical bridge adorned with decorative dragons.

Inspired by the Rialto Bridge in Venice, these three clustered bridges were just one part of a Slovenian architect’s grand vision.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

The largest fountain in Bratislava.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

An underground city beneath Krakow's postwar socialist utopia.

This sprawling concrete suburb of Kraków was designed by the Soviet Union as the model proletarian city.

An underground city of salt.

The former Nazi Germany concentration camp stands as a museum to remember this dark chapter in European history.

This medieval village clings to a cliff in southwestern France.

Though this bridge was originally built in the 12th century, only one of its 10 arches dates back that far.

This library dates back to the late 17th century and was one of the first public lending libraries in England.

An unlikely link between a quiet English town and Sydney’s skyline.

A rather grand, but tiny, folly on the banks of the River Wear associated with a Polish count.

The National Railway Museum in York is the largest railway museum in the world, attracting almost 1 million visitors per year.

This sculpture marks the spot where one of the greatest Roman rulers was proclaimed emperor.

Follow the original medieval paths that wind through this intriguing section of the city.

The highest peak in Wales is said to be the final resting place of a giant killed by King Arthur.

What was once the world's second largest slate quarry is now a surreal post-industrial landscape

Austrian and Germans who died on British soil during World War I and II are buried here.

Parts of this former military training ground may have inspired parts of J.R.R. Tolkien's famous fantasy series.