Visiting the Hiroshima Peace Memorial is a "must" when in Hiroshima. Exhibits are beautifully & tastefully presented, even though seeing remnants of the bombing (e.g. personal belongings of school children etc.) can be upsetting. One of my favorite exhibits is the area devoted to Sasaki Sadakoh, including some of the tiny paper cranes she made from medicine wrappers. I recommend spending around two hours here in order to see/absorb everything. Located in Hiroshima Peace Memorial Park, the purpose of the museum is to document the atomic bombing, as well as to promote world peace.