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

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

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

This hunter-gatherer architecture is believed to be the oldest religious complex known.

These tombs were built into the side of a mountain so that ancient angels could reach the dead.

A marvel of Byzantine engineering under the streets of Istanbul.

Christianity and Islam have clashed, yet here a Serbian Orthodox church and a mosque stand together.

A futuristic, brutalist masterpiece that is also strangely prison-like.

This misspelled graffiti reappears every time it is removed.

This building featuring Brutalist architecture has a rich media production history.

The tallest lighthouse in the Nordic countries was also the site of a bloody World War II battle.

These 5,000-year-old cave paintings provide a glimpse into prehistoric Finnish life.

Every summer, an open-air swimming pool appears at the base of a Finnish city's beloved winter attraction.

This abandoned villa of makeshift buildings was once the home of dancer Elis Sinistö.

Finland's northernmost zoo is home to the country's only polar bears.

This cairn marks the only place where Central European Time, Eastern European Time, and Further-eastern European Time meet.

This modernist island church incorporates the Finnish nature into its worship practices.

A long-disputed lighthouse built on the wrong side of a Finnish/Swedish island.

A cathedral resurrected from the ashes of one of Europe's greatest urban fires.

A lumberjack in Finnish Lapland did not want to cut down his Arctic pines, so he offered them up to be adopted by nature-lovers.

Fortifications built for a Soviet invasion that never came now sit abandoned in a losing battle against nature.

This lonely rock has been turned into a character loved and feared by children.

Nuclear waste experts study this prehistoric crater lake to envision landscapes one million years in the future.

If you visit Santa's village, you can get your passport stamped to show you crossed into the Arctic Circle.