“To keep it stable, hundreds of employees have to work around the clock, pumping a cement mixture into the earth below. Without continuous maintenance, the rock beneath would wash away, causing the dam to sink and then break apart. But Iraq’s recent history has not been conducive to that kind of vigilance.” And if it fails, a million and a half lives could be at risk. The New Yorker’s Dexter Filkins on the Mosul Dam: A Bigger Problem Than ISIS?