Go inside to really appreciate this 500-year-old technological masterpiece.

A minotaur, a labyrinth, and a dubious restoration pull in visitors from around the world.

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

The hallucinogenic center of the ancient world.

These Egyptian statues have survived for 3,400 years and were an acoustic wonder of the ancient world.

One of the most well-preserved temples of ancient Egypt.

This daunting 1st century fortress was purportedly the site of one of the most dramatic revolts of the Jewish-Roman wars.

An ancient capital city that dates back 3,000 years old and harbors many surprises.

Ruins of the Crusaders' headquarters.

Mysterious lost empire of the Silk Road.

One of the largest ochre quarries in the world, hidden in a limestone landscape.

This newly renovated Soviet-era outdoor exhibition center is bigger than the principality of Monaco.

Moscow's imposing monument to the Space Age.

A 250-year-old timepiece-automaton adorned with golden mechanical birds, which still sing to this day.

An 18th century wonder of the world, lost in WWII, re-created at the Catherine Palace.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

A museum dedicated to the former country.

A pair of connected skyscrapers form this symbolic gateway.

A Serbian church lit by chandeliers made of weapons.

Nikola Tesla's ashes are held in a golden sphere, surrounded by his works.

A wunderkammer of gold and silver reliquaries and ancient saintly bones.

A trough of 700 strange bronze faces runs through a narrow alley in Ljubljana's old town.

A whimsical bridge adorned with decorative dragons.