Roman ruins top white travertine terraces formed by ancient hot springs.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

The true depths of these stunning Moroccan caves are unknown.

Traditional 11th-century outdoor tannery.

The other side is actually green.

Founded as a refugee camp, now a popular tourist spot.

Morocco's Argania trees are infested with nut-hungry goats.

The site of the first battle of World War II.

Naturally formed rock city in Poland.

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

This uber-quaint Polish village is known for its habit of painting elaborate floral motifs on just about everything.

This Polish cave has housed a dragon, a brothel, and an enduring legend.

This Nazi ruin was the site where Hitler was almost blown up by a suitcase bomb.

Countless stories attempt to explain Poland's mysterious J-shaped trees.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

The United States Capitol's former columns still stand.

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

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

A whimsical bridge adorned with decorative dragons.

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

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

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