f The Forgotten Holocaust in Lithuania - Geophysical Investigations at the Ponary Extermination Site

Prior to the Nazi invasion of Lithuania in 1941 and the temporary retreat of Soviet forces, the country and its capital city, Vilnius, were home to a thriving Jewish community of just over 200,000 people. During the Holocaust more than 95% of Lithuania’s Jewish population was massacred by German and Lithuanian killing squads. Of those killed some 70,000 Jews, and a further 30,000 Poles, Russian POWs, and political dissidents were exterminated at a single site within the Ponary (or Paneriai) forest, near Vilnius. Here, a series of circular pits, originally intended for fuel storage by the Soviets, were used as mass graves. Because investigation of the site was actively discouraged during the post-war Soviet era, our understanding of the Ponary massacre is largely limited to survivor testimonies and a few eyewitness reports. Furthermore, since the surviving local Jewish community is sensitive to the further desecration of human remains at the site, traditional archaeological excavation methods have been largely prohibited at the site. Non-invasive geophysical methods can therefore provide useful information to document the past history of the site in lieu of and prior to targeted archaeological excavations. In 2016 we undertook a geophysical survey at Ponary using electrical resistivity tomography (ERT), ground-penetrating radar (GPR), and aerial drone imagery techniques. We describe the results of the 2016 geophysical investigation, including the delineation of an unmarked mass grave and the discovery of an escape tunnel, through which 11 Jewish slave labourers survived the Holocaust to tell the story of events at Ponary. By combining the results of our geophysical survey with interpretation of historical air photos and a LiDAR digital elevation model, we show how non-invasive geophysical and archaeological techniques can be used to reveal key details of the Ponary massacre and preserve the history of the Holocaust in Lithuania.