Hiroshima's Peace Memorial Park (平和記念公園, Heiwa Kinen Kōen) is one of the most prominent features of the city. Even visitors not looking for it will likely stumble upon the large park of over 120,000 square meters. Its trees, lawns, and walking paths are in stark contrast to the surrounding downtown area.
Before the bomb, the area of what is now the Peace Park was the political and commercial heart of the city. For this reason, it was chosen as the pilot's target. Four years to the day after the bomb was dropped, it was decided that the area would not be redeveloped but instead devoted to peace memorial facilities. https://www.japan-guide.com/e/e3400.html