This 1967 experiment in modular architecture was designed to be a new model for urban living.

Its columns were all carved from the same white oak tree.

City law dictates that this mountaintop cathedral containing the heart of a saint is to remain the tallest building in town.

This North African stone complex is considered to be the oldest astronomical observatory on Earth.

A nun spent 16 years painting the stunning Celtic mural that covers the interior of this WWI memorial.

A Gothic cathedral created from volcanic rocks.

Poland's oldest salt mine has nearly everything one needs to live underground forever.

The inverted pyramid design of this station stands out amid Bratislava's urban landscape.

Also known as the Blue Church, the building was consecrated to the daughter of Andrew II.

This spaceship sculpture in the middle of the Slovakian capital looks like it just crash-landed.

A once-fairy tale mansion now stands in a state of disrepair.

The 3.8 billion-year-old rock proves that tectonic plates may have been shifting longer than we thought.

Greenland's first shopping mall also hosts the country's government.

Thousands of letters to Santa get delivered to this mailbox in Greenland.

These eight mummies are the best-preserved human remains ever discovered in North America.

1% of Greenland's entire population used to live in this single building, which is now slated for demolition.

A tropical paradise once home to space exploration and military installations.

Once a strategically imperative naval base, portions of this Bermuda dock complex now serve cruise ships.

In Bermuda, this formal naval residence has become a go-to for cliff-jumpers and hikers.

Where a rare geological phenomenon created a section of rock that resembles a checkerboard.

Storms, funding, and in-fighting have kept this Bermuda church from ever being completed.

A fire station-turned-church-turned-museum dedicated to the work of seminal light artist Dan Flavin.

The largest underground lake in Europe.

The abandoned grounds and derelict greenhouses of this once-magnificent Edwardian estate are now a nature preserve open for exploration.