The ruins of this medieval castle in Northern Ireland have inspired artists from C.S. Lewis to Led Zeppelin.

This short bridge is the only thing connecting a tiny Irish island to the mainland.

Northern Ireland's Brobdingnagian stepping stones.

These barriers stand as stark reminders of Northern Ireland's troubled past.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

Single runway interrupted by a busy road that cuts across its middle.

Sofia's legislative center is continuously reinventing itself.

A gigantic statue of a Russian soldier watches over the ancient city of Plovdiv, a prominent reminder of the Soviet period in Bulgaria.

A vast Communist-era exhibition space in the Bulgarian capital.

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

This ancient theater, restored in the 20th century, lives on as a venue for dramatic and musical performances.

A collection of art from Bulgaria's time as a communist state.

A striking symbol of the Bulgarian capital.

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

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

Meant to be a lavish presidential home, the palace became a symbol of the fall of South Vietnam.

Giant pagoda houses the car that drove Thích Quảng Đức to his death by self-immolation.

The topiary maze at the Habsburg hunting lodge.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

This series of Baroque passageways in Vienna's cultural center mix old architecture with modern art.

A neo-Gothic church built to thank God for saving the Emperor of Austria from an assassination.

The Habsburgs' royal collections of art and wonders.

The art museum is decorated with creatively remodeled pre-Nazi swastikas.

The largest bottled beer collection in the world holds over 22,000 unique beer bottles.