Sightseeing>Vicinity>Hiroshima
Hiroshima
A-bomb dome
Hiroshima is the first atomic-bombed city. 
Some countries have nuclear bombs with the purpose of use. I wonder if they could still keep their policy after they visit Hiroshima and learn what happened and still happening there. People in Hiroshima are still suffering.
Although most Japanese don't have grudge against Americans, people in Hiroshima never forget Americans for doing wrong things, as long as Americans say that they did the right thing.
http://www.pcf.city.hiroshima.jp/
You'd better study the fact before you visit the museum.
Miyajima Island
After visiting A-bomb dome and peace memorial museum in Hiroshima, I recommend you to visit Miyajima and enjoy the rest of the day.
On the Island, a beautiful shrine stands, but this is not my main visit.
My strong recommendation is going up to the summit of Mt. Misen.
Cute monekys and wild deer are waiting for you.
http://www.miyajima-island.com/flash/english/welcome.html
You'd better check the high water time so that you can see Mont Saint-Michel-like shrine.
Shukkei-en
If you don't have time to go to Miyajima, go to Shakkei-en. This is the garden appreciated by Samurai lord.
250yen
http://shukkeien.jp/ (only in Japanese)