A small town in Poland. On July 19, 1941, half of the town murdered the other half--1600 men, women, and children--all but seven of the town's Jews.
The most horrible thing about the massacre is that the Jews of Jedwabne were not killed by faceless Nazis--although the town was occupied, the soldiers limited themselves to advice--"Kill them slowly, let them suffer"--but by people they knew, their neighbors.
"Why", asked a columnist in a national newsmagazine after the book "Neighbors" was published, "did the Poles of Jedwabne kill their neighbors? Because it was permitted. Because they could."
See "Neighbors: The Destruction of the Jewish Community in Jedwabne", by Jan Tomasz Gross.