The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

Ancient ruins hidden underneath a modern luxury hotel.

Breathtaking and huge 430 year old maps of Italy.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

This angular Dwarven tunnel cuts through a mountainside in Glacier National Park.

The only road through the heart of Glacier National Park.

An American city stranded at the tip of a Canadian peninsula where strict adherence to the "49th parallel rule" became problematic.

The entire length of the border is marked by a 20-foot-wide slash through the trees.

Five candy-colored villages on the Italian Riviera.

A lover's walk between hilltop towns, decorated with graffiti love notes.

Pilgrimage site for star-crossed lovers.

The fairy tale castle of the "fairy-tale king."

Two stone columns flank the grand Venice square, but there were supposed to be three.

Go inside to really appreciate this 500-year-old technological masterpiece.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

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

The blood-soaked ruins of the castle where the murderous Blood Countess was walled in alive.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

American soldiers discovered Europe's best one-liner at the end of World War II.

Go surfing on this urban wave, "hacked" by local surfers.

The history and future of cannabis.

Eighty million natural history specimens call this gargantuan museum home.

This innovative steam machine was no doubt the most famous of the pioneer locomotives.