Why to go: The bomb that destroyed Hiroshima killed half as many people as the fire-bombing of Tokyo by conventional weapons only a few weeks before. But the terrible difference was that the Tokyo bombing had taken hundreds of planes to carry out. Hiroshima’s executioner was a single bomber, accompanied by a plane sent to film the bomb’s explosion.

By August 1945, an exhausted world believed that warfare had finally reached its apex in the unbridled firepower that had distinguished WWII. Surely the poison gas of the Nazi death camps, the massed artillery of the Red Army and the napalm bombs dropped on Tokyo marked the limits of ghastly weaponry.

They didn’t. In one millisecond the fission weapon dropped on Hiroshima changed everything. The specter of total destruction, complicated by radioactive poisoning, now entered the consciousness of all people, civilian and military. A bomb the size of a small car could incinerate a dozen square miles in an instant, and poison dozens more. Total war between two countries could now be waged and ended in the space of a few hours or days, with the prospect that both belligerents would be plunged into a dark age of disease, starvation, anarchy and suffering.

Remarkably, despite being directly under Ground Zero, the Prefectural Hall was not totally destroyed. The Americans designed their bomb to detonate 1,800 feet above its dome, intending to create an air burst that would disperse the terrible power of the bomb over the maximum possible area. After the calamitous explosion, the building, stripped of the skin on its dome, remained as a mute witness to the events of August 6, 1945.

It would become the centerpiece of the world’s first monument to the power of nuclear war. Over the years a stream of pilgrims, from Japan and nations all over the world, have come to Hiroshima to see the building and often use it as a backdrop for anti-war activities. Almost 58 years after the super-brilliant dawn of the atomic age, the bare ribs of the Prefectural Industrial Promotion Hall form the image that comes to mind in hundreds of millions of people when they think of mankind’s closest brush with the abyss.

What to add to the journey: Hiroshima spills down to the sea, its city center riven by five major channels that run through it inland from the sea like the canals of Venice. It is a beautiful, lush, temperate part of Japan. Offshore, Miyajima Island in Hiroshima Bay is a World Heritage Site. It is the setting for an old Shinto whose tori, ceremonial gate, has become the symbol of Japan in the minds of millions.