In a grassy patch of public park in central Warsaw last week, archaeologists dug up a rusted metal coat hook and the tangled chain of a decayed necklace. The objects couldn't be more ordinary. Or more extraordinary. The team excavated them from the buried rubble of the Warsaw Ghetto, where German occupiers sealed hundreds of thousands of Poland's Jews into crowded, desperate squalor during World War II and over 80,000 died inside the walls of starvation, exposure and infectious diseases. Amid the twisted metal and bits of glass, the archaeologists unearthed small, unassuming remnants of daily life, suspended in hardened...