The Germans established a number of death camps: Belzec; Sobibor; Majdanek; Treblinka; Chelmno, which was the center from which death trucks operated; and Auschwitz-Birkenau.  Belzec, located in southeastern Poland, was the first death camp to become operational.  In the course of its one year of mass gassing of Jews from Southern Galicia and the Lublin district, it is estimated that 600,000 Jews were murdered.  The second death camp to begin operation was Sobibor, built in eastern Poland for the express purpose of being a death camp.  In a year and a half of operation, 250,000 Jews perished in Sobibor.  In July 1942, Treblinka went into operation.  Its prime purpose was to exterminate the inhabitants of the Warsaw ghetto.  Between 700,000 and 1,000,000 Jews died in the gas chambers of Treblinka.  Majdanek was built right outside Lublin.  It was both a work and death camp.  One hundred twenty-five thousand Jews were killed at Majdanek.  The largest of the death camps was Auschwitz.  Auschwitz was in fact of series of 34 camps, most used for slave labor.  Birkenau, a separate camp within the complex, was the death camp.  Trains would arrive from throughout Europe with Jews inside. Upon their arrival, the Jews were forced to pass a selection process, often conducted by Dr. Josef Mengele.  Those who were fit or had special skills were directed to the labor camps.  The others, including all the children, were sent to the gas chambers.  There, in the guise of preparing for a shower; they were forced to undress, and then enter a closed chamber.  When they were all inside, the doors would be closed, and Zyklon B gas dropped in the chamber.  Within a few minutes, all of the Jews would be dead, and their bodies would soon be brought to the crematoria for burning.  All together, 800,000 Jews met their death in Aushwitz.