This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

This 14th-century monastery survived Turkish raids, Nazi occupation, and even a stint as a spot to store towels.

A relic from the Industrial Revolution got a second life as a contemporary performing arts space.

Colorful power station with a chimney equipped with a gallery for exhaust monitoring equipment.

A whimsical bridge adorned with decorative dragons.

This abandoned Slovenian military barracks has become a punky-political art squat.

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

This exquisite example of early colonial architecture remains unfinished almost 500 years after construction began.

An unusual resting place built into the hill with an amazing view of Lake Como.

Half-hidden by grassy slopes, this striking Spanish colonial fort is now a museum of underwater archaeology.

A cooled lava flow from the Haleakalā volcano formed these surreal-looking columnar basalt structures.

An early 20th-century sanatorium, long abandoned and now being reclaimed by nature.

In the quiet village of Fulmodestion, the ruins of a medieval church remain hidden among vines and foliage.

This historic Mexican convent is home to a tree that grows crucifix-like thorns.

Trek through the jungle on a boat and a swinging bridge and you'll be rewarded with these refreshing, if pungent, mineral pools.

This piece of a Renaissance-era Spanish castle remained lost for decades.

This small gallery nestled inside an old botanical glasshouse is a quiet place to enjoy art and nature.

The state bird of New Mexico, constructed entirely out of garbage.

The first public library in the Americas has more than 45,000 books dating back to the 15th century.

For part of the year, this innovative greenhouse is painted white to keep the plants from getting scorched.

This recessed garden protects thousands of mountain plants by creating its own microclimates.

An ornate private entrance to the Vienna subway built specifically for the emperor.

The sanctuary seems to either float atop the water or sink into the dirt, depending on the water level.

Climb to the top of its spiral spire for spectacular views of Copenhagen.