Travel back to London and the tunnel network that has existed since Victorian times.

Discover the tunnels that made the Battle of Okinawa so difficult.

Travel to Sicily to trace the mafia's roots back to a vigilante secret society in an underground network that was created to hold trials against corrupt city officials and execute the accused.

Journey to the secret underground of Las Vegas.

World War I was the bloodiest war the world had ever seen. A young Adolf Hitler served in the trenches and tunnels of Belgium's Western Front. Explore the subterranean web where 24,000 Allied soldiers waited to ambush the enemy, to the indestructible fortress that endured thousands of bombs daily. Discover the underground that made World War I one of the most brutal wars in history and turned Hitler into the terrifying madman of World War II.

After the fall of the Roman Empire, Europe was plunged into chaos for centuries, with vicious carnage and rampant disease regularly raging through the streets. However, below the streets was another world designed to keep the people alive and the enemy guessing

He was the mastermind of the most notorious cuddles in U.S. history. He terrified the world and plunged the city of Los Angeles into a state of paranoia and fear. He's Charles Manson, and the deserts around Los Angeles were his home--where he hoped the underground would be his haven. But Manson and his followers weren't the only dangers lurking beneath the streets of LA.

The gladiators of ancient Rome were the ultimate fighting machines. They waged bloody battles to the passing for the entertainment of the masses--and to earn their freedom. From the depths of the vicious and magnificent Flavian amphitheater, to the buried brothel where they lived their last days, these are the secret lives of Rome's famed slave warriors.

Ethiopia is home to some of the oldest settlements in the world. This cradle of mankind is a country born from legend and shrouded in mystery. An ancient home to both Jews and Muslims, Ethiopia is also the world's second oldest Christian nation. But if you were a Christian during ancient times, and if you wanted to stay alive, the only place to practice your faith was underground.

While most people think of San Francisco as a haven for peace-loving hippies, this city by the Bay is actually one of the biggest military defense installations in America. Go beneath its picturesque hills and uncover the biggest ammunitions depot on the West Coast before plunging into a deadly arsenal that once stored nuclear missiles with more than six times the destructive power of the atom bomb dropped on Hiroshima. From the secret Civil War fortification buried beneath Alcatraz to the human trafficking tunnels winding below Chinatown, San Francisco's underground is evidence of its sordid past.

The urban sprawl of Cairo, Egypt belies its history as one of the world's oldest civilizations, where the Pharaohs' ancient secrets lay hidden deep below the vast deserts of the Nile. Explore the massive engineering might of the oldest structures in the world, and learn how they survived a long history of invasions by the Greeks, Romans and Turks.

Lying at the crossroads of the East and West, Turkey has a history marked by conquest and conflict. Empires clashed over this land and its trade routes, leaving behind a rich mythology of gods and men, and tales of epic battles that soaked Turkey's soil in blood.

An exploration of the underworld of Sydney, including a 19th century prison, caves which were used by fugitive outlaws, and gold mines. Also, tour of a WWII chemical weapons storage facility, along with the people who once lived there.