The Nazis left no evidence behind at the Treblinka. After gassing an estimated 900,000 Jews and an unknown number of Roma in the camp in eastern Poland, Germany bulldozed it in 1943 and even planted crops and built a farmhouse on the leveled site. What was known about Treblinka came from the testimony of survivors who'd passed through it and that of captured guards.
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But now a great deal of physical evidence has been uncovered, NBC News reports. Archaeologists have found bones from mass graves, the "bathhouse" where victims were gassed, and even tiles stamped with Stars of David used to lull Jewish prisoners into thinking they were safe.
The archaeological team, led by Caroline Sturdy Collis of Staffordshire University, worked for six years using computerized maps, aerial photography, GPS technology, ground-penetrating radar and a laser-scanning technology – which allowed them to go underground without unduly disturbing the site.
After the war, Treblinka was turned into a memorial, and excavation of the site was forbidden. But Sturdy Collis persuaded Polish and Jewish religious authorities to let her team conduct a "limited dig" that would be largely non-invasive.
"Without that technology, I never would have been able to do this work at Treblinka, because no one wanted excavations there," Sturdy Colls said. "Nobody wanted the ground to be disturbed unnecessarily."
After uncovering the remains and examining them, the archaeologists put them back in place and restored the site to its previous condition and appearance.
"What we were doing there was closing the lid again on that grave site. ... It didn't cross my mind that it would be me reinterring the remains," Sturdy Collis said.
The story of the archaeologists' investigation and findings will be told in the hour-long documentary, "Treblinka: Hitler's Killing Machine," airing Saturday on the Smithsonian Channel.