This memorial park stands on the site of one of the largest mass executions of the Second World War.

Structure built from the skulls of vanquished foes.

A museum dedicated to the former country.

A towering spire in the fortress of Kalemegdan honors the victorious armies of Serbia during their struggles against the Ottoman Empire.

A Serbian church lit by chandeliers made of weapons.

A pair of connected skyscrapers form this symbolic gateway.

A retro Yugoslav congress, cultural, and business hall built in the 1970s, with an iconic world clock.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

Stone age urban planning.

A Roman monument to their own civil engineering prowess.

Imperial palace of Emperor Galerius, the Emperor behind the worst Christian persecutions during the Roman Empire.

A small, but very well curated, museum of cars, propaganda, and toys of socialist Bulgaria.

A massive cave once a secret military base is now home to thousands of bats.

Sofia's legislative center is continuously reinventing itself.

These cascading falls resonate throughout the Bulgarian forest.

The remarkably well-preserved final resting place of a powerful ancient Thracian king.

A mountain pass in Bulgaria's Balkan Mountains was the site of four historic battles.

A magnificent, glittering building tucked into a tiny Bulgarian mountain town.

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

Underneath this Byzantinian church lies a necropolis filled with ancient tombs and the ruins of previous churches.

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.

UNESCO-protected ancient burial ground.