Roughly 17 million letters to Santa have found their way to this Arctic Circle post office.

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

A subterranean house of worship carved right out of the bedrock.

Architecturally stunning library serves as the hub of Finnish scholarly life and culture.

An alien church provides much needed silence in the midst of a Finland shopping center.

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

This beautiful Croatian fortress is haunted by legends of forbidden love.

A well-worshipped shrine to the Virgin Mary nestled inside the last of Zagreb’s historic gates.

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

Despite the name, the waters of this Canadian lake are actually blue-green in color.

The metal truss bridge served as the sole entry point to an "isolation island" for smallpox outbreaks throughout the 1870s and early 1940s.

Take a dip beneath the stalactites in this amazing cenote.

Underwater art project will double as a massive artificial coral reef to help regenerate the damaged ecosystem.

In Costa Rica's cloud forest, the roots of a woody ficus create a botanical bridge.

Sloth rehabilitation center in the jungle of Costa Rica.

A park that allows you to get up close and personal with one of the world's largest open volcanic craters.

This collection of historical artifacts and tropical wildlife waits just beneath the surface of the water.

A mysterious architectural gem in one of the most elegant areas of Buenos Aires.

A pocket of serenity in hectic Buenos Aires, complete with a peaceful courtyard and massive library.

The most southern point you can drive to in the Western Hemisphere.

The best place to send your postcards home from Antarctica.

The largest piece of no man's land left on Earth.

This 7th-century monastery was sacked by Saladin.

A stunning fusion of Ottoman and Fatimid architectural styles.