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

A fountain standing as a testament to a doomed alliance.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

A marvel of Byzantine engineering under the streets of Istanbul.

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999.

Baroque celebration of the end of the Great Plague of Vienna.

A surreal statue honoring Prague's favorite literary son.

Looming communist pillar with a Czech twist.

Large Hadron Collider and the Birthplace of World Wide Web.

Sweden's "good old days" painstakingly re-created in a model village.

It houses the remains of a 17th-century version of the Titanic.

The ruins of this Dutch castle sit atop a labyrinth of once-secret tunnels and passageways, dating back over 900 years.

Visit the ancient, mysterious Roman catacombs ... in the Netherlands.

This sprawling Belgian fort was once thought of as impenetrable but now it is simply an abandoned relic.

Incredible labyrinth of man made caves.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

A collection of biblical memorabilia.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

A fascinating insight into daily life in the Eastern Bloc.

Possibly the oldest church in Barcelona, this basilica has its pagan and Christian mythologies all mixed up.

The golden Buddha statue at the Wat Muang Monastery is the tallest in Thailand, and the ninth-tallest in the world.