Hiroshima divides naturally into two parts: the memorial landscape around Peace Park, and the rest of the city that has quietly rebuilt itself. Both are worth your time.
The Peace Memorial Park occupies the triangular sandbar where the Motoyasu and Honkawa rivers meet — the area once known as Nakajima, which was directly below the hypocenter. The park's monuments are arranged along a single axis. Stand at the Cenotaph for the Victims and look through its curved stone arch: the flame of peace burns in the pool before you, and the A-Bomb Dome stands framed in the distance exactly as intended. The dome — the only structure left standing near the hypocenter — was a deliberate choice. Its gutted skeleton is the most powerful thing in the park.
The Hiroshima Peace Memorial Museum is one of the essential museums in Japan. It does not flinch. The exhibits show in specific, unflinching detail what a nuclear weapon does to a city and its people — burned clothing, melted roof tiles, the shadow of a man etched into stone steps. Allow two hours minimum. Entry ¥200.
Away from the Peace Park, Hiroshima Castle — destroyed in 1945 and reconstructed in 1958 — houses a good museum on the castle town and samurai culture. The moats and gardens around it are pleasant to wander.
Shukkei-en is a miniature landscape garden dating to 1620, compressed into a small space so that hills, bridges, and islands create the impression of a much larger scene. Damaged in the bombing, it was restored; an unusual survivor.
Across the bay, Miyajima is a 10-minute ferry ride from Miyajimaguchi (tram Line 2 from the city centre). The Itsukushima Shrine's orange torii gate standing in the water at high tide is one of the most recognisable images in Japan. The island is small enough to walk, and the deer are genuinely tame.