Chelmno
During the German occupation not a lot of people in Poland knew of Chelmno's existence. It was located in the villiage of Chelmno, close to the town of Kolo where the main railway line runs from Lodz to Poznan. The whole enclosure was only 5 acres and inside the enclosure were two buildings, a small country house, and old granary and two wooden hutments the Germans constructed.
Those that came to Chelmno thought the whole time they were to be employed on fortification work in the East. When the time came for them to be gassed they were told that they were getting a bath and that their close were being disinected. They were taken to the large hall of the house and were told undress and then driven along a corridor to a large wagon was standing. The wagon was made up to be a gas chamber with pipes connecting carbon minoxide into it. They would be locked inside the wagon and after 4 to 5 minutes, until all the people were dead inside, and drive to the woods to bury the corpses.