If you have only one full day, keep the focus on Hiroshima City rather than automatically combining the city and Miyajima. The official city course connects Shukkeien, Hiroshima Castle, the Atomic Bomb Dome, the Peace Memorial Museum and the National Peace Memorial Hall, showing that the central city alone can fill a meaningful day.
Make the Peace Memorial Museum the fixed point in the schedule. Its web-ticket and reservation rules can change by date, and certain periods or time slots may require advance booking. If you secure an early entry, visit the museum first and walk through the park afterward. Otherwise, begin with the Dome and park monuments, then enter at your reserved time.
Allow roughly three to four hours for the complete peace area if you plan to read carefully, visit the museum and National Peace Memorial Hall, and walk the memorial axis without rushing. That is an editorial planning range, not an operator promise. The emotional intensity of the museum also makes a quiet meal or riverside break more useful than immediately racing to the next attraction.
After lunch around Otemachi or Hondori, continue to the castle grounds and Shukkeien if time and energy allow. The castle keep is now exterior-only, so the stop is shorter than older guidebooks suggest, but the Ninomaru and surviving historical landscape still reward an informed visit. End with dinner around Hondori, Nagarekawa or Ekinishi.
A late arrival changes the decision. Do not compress the museum into the final hour merely to keep every item. Drop the castle or garden first, preserve the peace sites as the day's center, and confirm the museum's current last entry before setting out.
- Early: reserved museum entry, or the Dome and park monuments
- Late morning: complete the remaining peace-related sites
- Lunch: Otemachi, Hondori or Kamiyacho
- Afternoon: Hiroshima Castle exterior and Shukkeien
- Evening: Nagarekawa for nightlife or Ekinishi for station convenience