 The third section of Treblinka II (Camp 3, also called the upper camp) was the main killing zone with gas chambers at its centre. It was completely screened from the railway tracks by an earth bank built with the help of a mechanical digger. This mound was elongated in shape, similar to a retaining wall, and can be seen in a sketch produced during the 1967 trial of Treblinka II commandant Franz Stangl. On the other sides, the zone was camouflaged from new arrivals like the rest of the camp, using tree branches woven into barbed wire fences by the Tarnungskommando (the work detail led out to collect them). From the undressing barracks there was a fenced-off path leading through the forested area into the gas chambers. It was cynically called die Himmelstraße ("the road to heaven") or der Schlauch ("the tube") by the SS. For the first eight months of the camp's operation, the excavator was used to dig burial ditches on both sides of the gas chambers; these ditches were 50 metres (160 ft) long, 25 metres (82 ft) wide, and 10 metres (33 ft) deep. In early 1943, they were replaced with cremation pyres up to 30 metres (98 ft) long, with rails laid across the pits on concrete blocks. The 300 prisoners who operated the upper camp lived in separate barracks behind the gas chambers.
