Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

Mysterious 500-year-old tapestries depict a unicorn hunt.

Legend says if you stick your thumb in the hole and it gets wet your wish will be granted.

A fountain standing as a testament to a doomed alliance.

The largest copper mine in Arizona, this enormous open pit emerges from the hills like an alien landscape.

After a short-lived attempt to bring America in line with the rest of the world, this road was left in metric.

Limestone caves with spectacular showcase chambers.

This historic national park is covered in the stunning ruins of red rock pueblos.

A historic observatory precariously perched at the "Top of Europe."

Ancient serpentine sacrifice holder that has stood the test of time.

1513 Turkish world map, full of European state secrets and snarky commentary.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

A marvel of Byzantine engineering under the streets of Istanbul.

The largest wildlife crossing in Utah allows local fauna to safely traverse the six-lane Interstate 80 at Parleys Canyon.

Few things look more out of place than the electric blue ponds in the reddish-brown desert of Utah.

The fifth-longest natural arch in the world, and the longest outside China.

"May the force be with you always."

A 90-foot-tall psychedelic "tree" on the side of the highway has baffled passersby for decades.

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 isolated outpost was once the only place to cross the Colorado River for hundreds of miles.

Stairs often replace streets on the steep slopes of this old mining town.

Witnessing the might of this dessert-colored desert waterfall is a rare, powerful treat.

A living snapshot of a different time in America is preserved and maintained by a community of volunteers.