Hiroshima’s downtown is a garden of modern architecture interspersed with swaths of lovely green parks. In the center is a single structure, in ruins, capped by a skeleton of curved iron. This is the Atomic Bomb Dome, located at the destruction’s epicenter, the sole building that managed to remain standing amid the massive force that flattened everything else for miles in all directions. It is an astonishing memorial to both our capacity for horrifying devastation and our awesome re…