Hiroshima's peace bell marks the 68th year of the city's entry into history for the most horrific of reasons.
Its residents observe a minute's silence at the exact time the atomic bomb fell in the closing days of World War II.
By the end of 1945 an estimated 140, 000 - more than a third of the population - lost their lives. Many died in the blast - more afterwards from radiation exposure.
Three days later the United States dropped a second atomic bomb on Nagasaki. Six days after that Japan surrendered.
Japanese Prime Minister Shinzo Abe, like many of his predecessors, spoke of Japan's duty to press for a world free of nuclear weapons.
This year's memorial comes at a time when Japan is pushing to sell its nuclear technology abroad despite opposition.
It also comes at a time when efforts to contain the aftermath of the Fukushima nuclear disaster after the 2011 earthquake and tsunami are not going well.
The company which operates the plant says radioactive groundwater is rising beyond its control.