The ancient necropolis houses the immense rock-cut tombs of four Persian kings.

The mysterious empty cupola behind the monumental arch points to an ancient prophecy of Delhi.

This grand hydraulic installation has provided water for townspeople since the Middle Ages.

The ancient heart of Tunis is an enormous maze of narrow streets and alleyways.

The best-preserved Roman small town in North Africa.

A bathhouse from the second Islamic Caliphate decorated with frescoes of constellations, pleasure gardens, and naked ladies.

This once-derelict building is now one of the most beautiful bookstores in the world.

This memorial to the victims of the Romanian Revolution of 1989 is often compared to a potato on a skewer.

Romania's triumphal arch looks out over Bucharest.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

Where Venice's gondolas go for a tune-up.

Thousand-year-old Viking runes adorn an ancient Greek lion at the entrance to the Venetian Arsenal.

Stare out over the lagoon and beyond from this 10th-century campanile on the island where the city of Venice began.

This building has two facades of clashing architectural designs.

Sofia's legislative center is continuously reinventing itself.

This massive stone and steel monument remembers a century-old battle that cost thousands of lives and nearly destroyed the city.

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

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

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.

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

Outstanding, eerie frescoes and decorations fill this 19th-century monastery.

A striking symbol of the Bulgarian capital.

UNESCO-protected ancient burial ground.