Hiroshima was the only place in Japan where I felt a little awkward as an American. Before I went, I was for dropping the bomb. Now that I've been there, I'm not so sure. Many people in the group were moved to tears by the exhibits in the memorial museum and the surrounding memorials. The things you shouldn't miss are the museum, the ground zero marker, and the A-bomb dome. If you're not crazy about history, Hiroshima is also as lively as any other Japanese city and you'll have no problem finding things to do. However, if you're going to a different city, like Kyoto or Tokyo, too, I suggest going to Hiroshima first because if you come back to it, it probably won't look/be as fun if you're not into the bomb history.