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

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

A striking symbol of the Bulgarian capital.

The only surviving choragic monument is a trophy awarded in 334 BC for the winning dramatic chorus.

The ruins of an ancient Roman tomb hidden in the basement of a trendy clothing store.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

A sharp sculpture made of thousands of pieces of jagged glass.

An ancient octagonal weather station named for the eight Greek gods of wind.

This mystical orb covered in strange symbols is thought to have been used in ancient Greek magical rituals.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

Monasteries on rock pillars, once accessible only by frayed ropes.