It’s a place where few living New Yorkers have ever set foot, but nearly a million dead ones reside: Hart Island, the United States’ largest mass grave, which has been closed to the public for 35 years. It is difficult to visit and off-limits to photographers. But that may be about to change, as a debate roils over the city’s treatment of the unclaimed dead. Never heard of Hart? You’re not alone—and that’s part of the problem.