Evidence of the apocalypse in Jerusalem; sacred stone.

Exploring Vietnam War-era tunnels, passages and secret caves used as shelters.

Underground technology protects Tokyo from natural disasters.

Exploring mysterious tombs, defense tunnels and an underground river beneath Dublin, Ireland.

Prague quarries and mines used for sinister purposes.

Explorers uncover Mayan tombs, sacrificial altars in the jungle of Belize.

Gangs, mob bosses, covert groups, and secret societies of early New York City.

Exploring the top secret underground defenses of Washington, D.C.

Deep within the former Soviet Union lays a classified.