The Nazis maintained more than 42,000 camps and ghettos across Europe, far more than had previously been identified, Holocaust researchers now say. For more than 10 years, historians at the U.S. Holocaust Memorial Museum have been compiling records of all the slave-labor camps, brothels, death camps, and ghettos set up from 1933 to 1945, mostly in Germany and Poland. Berlin alone, it turns out, had 3,000 such sites. “We knew before how horrible life in the camps and ghettos was, but the numbers are unbelievable,” said Hartmut Berghoff, director of the German Historical Institute in Washington, D.C. The documents cast new doubt on the notion that ordinary Germans did not know of the horrors being visited on their Jewish neighbors.