For centuries, the Lithuanian city of Vilnius was one of the most important Jewish centers in the world, earning the title “Jerusalem of the North,” until the Nazis destroyed it in World War II. About 95% of its Jewish population of Vilna, its name in Hebrew and Yiddish, was murdered and its synagogues and institutions were reduced to ruins. The Soviets finished the job, paving over the remnants of Vilna’s famous Great Synagogue, for example, so thoroughly that few today know it ever existed. Now, NOVA follows an international team of archaeologists trying to recover this lost world. They will excavate the remains of its Great Synagogue and uncover one of Vilna’s greatest secrets: a lost escape tunnel dug by Jewish prisoners inside a horrific Nazi execution site.