Background The Sobibor Extermination Center was one of three such secret death centers constructed during World War II in eastern Poland by the Nazis. Unlike such well known camps as Auschwitz-Birkenau and Majdanek that were concentration camps, labour camps, internment camps, etc., the three extermination centers of Treblinka, Belzec, and Sobibor were constructed in1942 for the sole purpose of exterminating the Jewish population of Europe. After disembarking from the rail platform in Sobibor, the life expectancy of a person was then measured in hours. At Treblinka, 850, 000 Jews were killed, with only about 40 surviving until the end of the war. At Belzec, 600, 000 Jews were killed, with only two survivors. At Sobibor, 250, 000 Jews were killed. At Sobibor, on October 14, 1943, about 600 Jews carried out a planned revolt. Of those, approximately 300 broke through the fences, trenches, and mine fields surrounding the center. And of those 300, only 52 survived until the end of the war. Following the breakout, and given the secret nature of the inhumanity prosecuted at Sobibor, the Nazis then proceeded to remove all physical evidence and traces of the center. Remaining prisoners were used to destroy the camp. The gas chamber was dynamited. Foundation piles were pulled from the ground. Other buildings, fences, and remaining structures were razed. Debris was burned and buried. A dense pine forest was planted where the camp once stood. Jewish labour used to destroy the camp was exterminated. Nazi staff were sent to the Italian front where many were killed. Most of the known air photos of Sobibor taken before 1944 were destroyed. Today, besides a small museum and monuments, there is little about the site to suggest that it is anything other than a bucolic destination for cyclists looking for a gentle ride in the countryside. From July 18 through July 23, 2008, geophysical surveys and aerial photographic investigations were carried out over portions of the site of the Nazi World War II Sobibor Extermination Center. The goal of the investigations was to provide subsurface reconnaissance information that would assist archaeologists in focusing their intrusive excavations. Specific tentative objectives of the surveys included delineating the boundaries of the extermination area of the Camp (Camp III), locating the gas chambers, delineating possible mass burials, locating individual subsurface features that may be precisely targeted by future intrusive investigations, and providing map coordinates for surface features that are known to be present in American aerial photographs taken in 1944 immediately after the destruction of the Camp. Two areas were investigated by the geophysical surveys. These included the several hectare open field around the prominent existing circular monument known as the hill of ashes, and eight 20 m X 20 m chained survey squares placed immediately south and east of the 2007 archaeological excavations. The open field was known to contain mass burials. The 400 m2 gridded area was suspected to be over, or in proximity to the gas chambers. Aerial photography was carried out over most of the original footprint of the camp. GPS data were collected at various locations on the original camp footprint, as specified by the archaeologists on site.