This historic black and white monastery is one of Bulgaria's architectural jewels.

The ceiling of Prohodna Cave in northern Bulgaria affords a peek at the sky via two deity-sized-eye-shaped holes.

Bizarrely shaped rock formations in northwest Bulgaria come with equally bizarre legends.

An abandoned saucer-shaped monument in the Bulgarian mountains.

This fortress dates back to the 6th century and is also the site of a controversial abandoned restoration project.

This 3,800-year-old site contains markers used to study the movement of the sun and moon and create a lunar calendar.

Space-age monument to an early 20th-century uprising.

A 11-foot former president stands on a Kosovo street that also bears his name.

A futuristic, brutalist masterpiece that is also strangely prison-like.

Oriental bazaar in the heart of Sarajevo.

The place where World War I began.

This museum preserves the hand-dug tunnel that kept Sarajevo afloat during the Serbian siege.

A war-torn Olympic relic is being overtaken by graffiti and nature.

Bridge that died in war and was resurected.

Ruins of the elaborate house where the enigmatic costume designer threw glamorous parties for New York's theatrical elite.

Ride the subways of yesteryear.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

This underground oasis is one of North America’s most fascinating prehistoric places—and you can scuba dive in it.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Florida might be at its most surreal in this museum devoted to the famed Spanish artist.

Frank Lloyd Wright’s most iconic home dangles over a Pennsylvania waterfall.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.