Hiroshima stands on a flat river delta, with few hills to protect sections of the city. The bomb was dropped on the city centre, an area crowded with wooden residential structures and places of business. These factors meant that the death toll and destruction in Hiroshima was particularly high.
The firestorm in Hiroshima ultimately destroyed 13 square kilometres (5 square miles) of the city. Almost 63% of the buildings in Hiroshima were completely destroyed after the bombing and nearly 92% of the structures in the city had been either destroyed or damaged by blast and fire.
Estimates of total deaths in Hiroshima have generally ranged between 100,000 and 180,000, out of a population of 350,000.
Due to the hilly geography of Nagasaki and the bombing focus being away from the city centre, the excessive damage from the bombing was limited to the Urakami Valley and part of downtown Nagasaki. The centre of Nagasaki, the harbour, and the historic district were shielded from the blast by the hills around the Urakami River.
The nuclear bombing did nevertheless prove devastating, with approximately 22.7% of Nagasaki's buildings being consumed by flames, but the death toll and destruction was less than in Hiroshima. Estimates of casualties from Nagasaki have generally ranged between 50,000 and 100,000.
The fact that the Nagasaki bomb was more powerful and also the narrowing effect of the surrounding hills did mean that physical destruction in the Urakami Valley was even greater than in Hiroshima. Virtually nothing was left standing.
