This is obviously a must to visit when in Hiroshima.  It is being preserved for perpetuity and that is a very good thing.  As well as seeing it in the daytime, try to go out at night when it is floodlit and also illuminated from the inside with orange lighting that makes it an even more powerful image and reminder of what happened in August 1945.  It is also less crowded at night.

When making a daytime visit, don`t miss the memorial to the students (some as young as 12) who were mobilised and killed by the explosion. This is near the Atomic Bomb Dome.

Another good idea is to travel to Myojima Island on the high speed ferry that goes from the pier just down from the Dome.  It takes a lot less time than the streetcar.  Travel back on the streetcar, so had a great round trip.