The World Heritage is a joint property of humankinds. Most of them have a universal value on human history, but some of them are the signs of bad happening. For example, Auschwitz Concentration Camp (Poland) and Hiroshima Peace Memorial (Japan) are symbolic places of World War 2.
Those properties have just a little historic value, but we have to treasure them to remember the wretched war, and let the war not to recur.
Focus on "Hiroshima"
A Thousand Orizuru (folded paper cranes) of Peace Memorial
At the time of eight fifteen on August 6 in 1945, a nuclear bomb bursted up above Hiroshima city. The bomb killed more than 140 thousand people.
Today, Hiroshima is a famous sight, which is a place remembered in connection with the miserable war, that is to say, we make it an amusement.
However, the people who have ever experienced the war have decreaced as the time passes. So, young people tend to forget the war although they have heard of it in school or from experienced people. Therefore, we should bequeath the eternal things about the war to the future with memory of it.