Hm, okay, interesting things in and around Hiroshima. I'll start with my official "guide" to day trips you can do with Hiroshima as a base. These are mostly things that I've done, and enjoyed thoroughly. They all assume that you are willing to and in fact enjoy to walk quite a bit (perhaps as much as 8 miles in one day.)
1. Catch a high-speed ferry to Matsuyama, ride the interurban and then the streetcar to Dogo Onsen. Assuming you don't mind getting naked in a public bathtub with a bunch of other guys, this place is not to be missed. Matsuyama is a great town. Don't cheap out and go just for the bath; go one step up, where they let you enjoy the resting room and some snacks. Lots of souvenier shopping potential in Matsuyama. This would be a long day, so get a start early in the morning.
2. Ride the train to Onomichi. It's a port and fishing town, you might not think there's much to see, but for two things. First, its udon is very famous (people will sometimes line up for blocks to get a seat at one of the popular restaurants). Second, there's an amazing park and a temple called Senkouji with a great view at the top of the mountain in the center of town. I recommend going on foot both ways, but there's a ropeway if you're not up to the hike. On my second visit, I borrowed a truck from my school, and a friend and I threw our bikes in the back and tried to
ride up to the top. Didn't work so well (fixed gear bikes) but the trip down was incredible!
3. Sandankyo. This is a mountain resort town. They had JR service up until November 2003, when the Kabe line was decomissioned beyond Kabe. I rode it a week before service ended and that train was
packed with people bidding the line "farewell." Now you have to ride a bus, which you can catch from the Hiroshima Bus Center (3rd floor of the Sogo department store, about a quarter mile walk down Aioi Doori from the atomic bomb dome). Sandankyo is especially beautiful in the fall, but springtime should be great too, and it's up in the mountains so it can be a great break from the sweltering heat and humidity of summer, too. And the fact that the train doesn't run up there anymore means that it will be less crowded!
4. Miyajima. This island is a popular destination for Japanese and foreign tourists alike. All the standard sights are great, but in addition to the touristy, settled areas of the island, you might also take a hike to the top of the mountain (the ropeway is nice, but I prefer hiking) or walk around to the back of the island, where they have a nice campground, a decent beach, and some more great hiking trails. If you go there from Hiroshima, take JR one way and LRT the other to get the full effect!
5. There's a steam powered train doing scheduled excursions in Yamaguchi prefecture, if you're into that sort of thing. They call it the SL Yamaguchi-Gou. I haven't ridden it, but I know said train makes stops in Tsuwano, which is picturesque little town.
There are more, of course, and there are also countless things to do that I
haven't done... but I don't want to overwhelm you
My guide to Hiroshima City will come later