This building, the Hiroshima Peace Memorial, is commonly known as the Genbaku Domu - Atomic Bomb Dome. The atomic bomb dropped on Hiroshima in 1945 exploded directly above this building. The building was preserved as a memorial. The surrounding area, devastated by the bombing, is now the Hiroshima Peace Memorial Park.
The image of this building, and its historical significance, is known around the world - familiar from school textbooks, TV documentaries, news reports, and so on. But it's a very powerful thing, standing in front of this building, being so close to it, studying its details. The reality of the event of the bombing becomes more tangible. If you are visiting Japan, I would strongly recommend that you need to make time to come here.
I apologise in advance if I'm tardy with commenting on your blogs or returning comments during the week... I will get to you though!