Hugged by rivers on both sides, this large leafy park is criss-crossed by walkways and dotted with memorials designed by Japan's pre-eminent modern architect Tange Kenzō. The Flame of Peace burns on the central pond and will only be extinguished once every nuclear weapon on earth has been destroyed. It's not an easy place emotionally, but it transforms grief into purpose, and the tree-shaded benches along the riverside offer moments of unexpected tranquility. On a sunny day, the contrast between the park's beauty and its terrible origin is overwhelming.