Uncover a vast underground city in Turkey that served as a refuge for Christians and Jews. Investigate a mysterious chalk chamber in England, visit a secret Etruscan complex beneath an Italian wine cellar, and map an ancient tunnel network in Iran.

Investigate a tomb in Naples that may contain a prince who inspired the legend of Dracula. Read the desperate letters of Jewish rebels hidden in an Israeli cave, tour a 6,000-year-old labyrinth in Malta, and see the oldest human burial in Africa.