What is the standing arch in Nagasaki made of?

Unbelievable structure!

At 11:02 a.m. on August 9, 1945, the explosion of an atomic bomb devastated Nagasaki.
The ferocious heat and blast indiscriminately slaughtered its inhabitants. Even the people who managed to survive continue to this day to suffer from late effects.

Five decades have passed since that day. Now the atomic bomb survivors are advancing into old age and their memories are fading into the mist of history. The question of how to inform young people about the horror of war, the threat of nuclear weapons and the importance of the peace is therefore a matter of passing concern.

The citizens of Nagasaki pray that this miserable experience will never be repeated on Earth. We also consider it our duty to ensure that the experience is not forgotten but passed on intact to future generations.

It is imperative that we join hands with all peace-loving people around the world and strive together for the realization of lasting world peace.

 The first bomb dropped on Hiroshima did not pull the Japanese into immediate surrender. Japanese warriors believed in honor, it was one of the most important things they believed. They thought it was a discrase to die in battle by their opponent. Japanese have avoided judging what is good or evil since ancient times, by trying to equal the "wrong" with disobeying the social order or going against authority.

 This explains why the ancient samurai warriors could take their lives to their god without having to think of how unmoral their actions were. They would rather end their own lives then letting the enemy take their own.

The bombs killed as many as 140,000 people in Hiroshima and 80,000 in Nagasaki by the end of 1945, roughly half on the days of the bombings. Since then, thousands more have died from injuries or illness attributed to exposure to radiation released by the bombs.
 In both cities, the overwhelming majority of the dead were civilians.

Six days after the detonation over Nagasaki, on August 15, Japan announced its surrender to the Allied Powers, signing the Instrument of Surrender on September 2, officially ending the Pacific War and therefore World War II. (Germany had signed its Instrument of Surrender on May 7, ending the war in Europe.) The bombings led, in part, to post-war Japanadopting Three Non-Nuclear Principles, forbidding that nation from nuclear armament.

On August 9, three days after the first bomb, Charles Sweeney, who flew the first B-29 bomber, flew another B-29 bomber into Japan. His original target was the city of Kokura, however, thick clouds covered the city making the bomb  too unclear to drop. Driven to his secondary target, Charles flew to the city of Nagasaki and dropped "fat boy", a 10,000 pound plutonium bomb, even more powerful than the first bomb dropped on Hiroshima, at 11:02 in the morning. It was estimated to produce a 22 kiloton blast,  Due to the hilly geography of the cities location, it drastically reduced the bombs explosion to about 2.6 miles.