Inside are floor-to-ceiling photos of Chinese civilians used for bayonet practice. Laughing Japanese soldiers behead prisoners; others are buried alive. A small boy is tied to a tree awaiting decapitation for selling candy. Women are shown mutilated. Everything is translated into English and, of course, Japanese.
Mass graves with thousands of bones also can be found inside. I rounded a corner and bumped into a knot of elderly men looking at a photo of a naked woman and a grinning Japanese soldier. Her face is a mask of dread and despair.
"See that?" one asked me in broken English. "Every Japanese should see that."
The fact that some Japanese deny or downplay the massacre remains a major irritant in relations between the two nations.
Still, there were heroes. I came across a statue of American missionary Minnie Vautrin, who saved 9,000 Chinese women at the Ginling Girls College in Nanjing.
There was a tribute to John Rabe, a German businessman who set up the Nanking Safety Zone and rescued 200,000 Chinese.
"History must never be forgotten. The Nanjing Massacre is a true tragedy for the Chinese nation, a natural humiliation. … It should forever be inscribed in Nanjing's memory," said a sign near the exit.
I came to Nanjing searching for insights into China through its history and now felt crushed beneath its weight.
Yet all around me life continued as it had for millenniums. Incense still burned in the temples. Old men still played lutes on Purple Mountain. Ships still plied the Yangtze.
And perhaps that was it. War, tyranny and suffering ebb and flow, but it is the resilience of a people that defines a nation.