Nazis hid the ashes of at least 8,000 Polish people in the Bialuty Forest in an effort to conceal war crimes. They even had other Jewish inmates plant trees on top of the remains. But decades later, investigators uncovered their secret: 17 tons of ashes were found in two mass graves in the forest, which is 100 miles north of Warsaw. Experts told the Associated Press that most of the victims were inmates of the Nazi’s Soldau concentration camp in the Polish city of Dzialdowo, killed in the forest between 1940-44. The forest has been known as a burial site for a while, but it wasn’t until this month that investigators found the exact spot where the graves lie.