A striking symbol of the Bulgarian capital.

An Albanian monument to the Communism that nearly crushed the country is now a crumbling wreck.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

As the highest point in the Mid-Atlantic range this stratovolcano offers spectacular views.

This monument to those fallen in the World Wars is accompanied by a U-boat that Germany bought for a Deutsche Mark.

Across this single-file rope bridge is what has been claimed to be the edge of continental Asia.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

The century-old bell and clock tower at UC Berkeley is the third-tallest in the world, and has fossils.

Once the largest windmill outside of Holland, with enormous 114 foot sails.

Millions of years of oxidation make a drive down this winding Death Valley road surprisingly colorful.

The lowest point in North America is home to an undrinkable pool surrounded by fields of geometric salt flats.

These markers are used to document elevation changes around the famed dam.

Local lore holds that Butch Cassidy took an escape route through Red Canyon's sandstone hoodoos after an attempted murder.

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

The unusual patterns in this rock formation result from two distinct modes of weathering.

A tunnel with windows, so you don't miss out on the impressive views.

An apocalyptic seismic event creates a deadly chain reaction that ends with a 6-mile long lake developing within weeks.

This rustic old building is said to be the most photographed barn in America.

This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

A beautiful geyser under environmental threat.

The 606 is a decade in the making.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.