The museum in the Park tells the story about the bomb on Hiroshima, but also about all the nuclear tests that were executed after that. I found this, and the rest of the Park, very impressive and tasteful.
Hiroshima itself is of course a very modern city, but I liked it a lot. It has a lot to offer, for example ... another World heritage! The Itsukushima Shrine is situated on an island in front of Hiroshima-City.