Explore a labyrinth built beneath Washington, D.C., by an eccentric entomologist. Admire a fresco-filled Roman mausoleum, spot intricate chambers carved into Colombia's volcanic rock, and see a sprawling network of hand-dug tunnels in Liverpool.

Examine a Revolutionary War-era ship found in the rubble of the World Trade Center. Uncover a mass grave of Viking settlers in Oxford, visit the resistance bunkers of the Warsaw Ghetto Uprising, and tour a necropolis full of burial jars in Corsica.