Structure built from the skulls of vanquished foes.

A Bulgarian monument to Russia's role in World War II is constantly being painted in pop culture protest.

A striking symbol of the Bulgarian capital.

Sofia's legislative center is continuously reinventing itself.

"Holy Wisdom" overlooks the city that became its namesake.

At 929 pounds and 26 feet tall, this stainless steel fork can only be used by the likes of King Kong.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

The site of a concentration camp where inmates were made to take part in one of the largest counterfeiting operations in history is now hauntingly empty.

A monument to the man who almost killed Hitler.

One of downtown Berlin's last reminders of its Communist past.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

A fascinating insight into daily life in the Eastern Bloc.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

10,000 flowered plants bloom in the City of Roses.

If drivers cross the rumble strip on this stretch of Route 66 at just the right speed it plays "America the Beautiful."

This museum started as a collection of Manhattan Projects and continues to add exhibits as they are declassified.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

Home of the International Space Hall of Fame.

This is one really big nut.

Twice a year, visitors can tour the desolate site that birthed the Atomic Age.

Twenty-seven massive radio antennas on the high plains of New Mexico search for life on other planets.

A one-of-a-kind sundial at the Very Large Array honors a radio astronomy pioneer, incorporating the original piers from his breakthrough radio telescope.

A striking 12th-century-style castle built on the edge of a cliff.