They had originally been barracks for the pre-war Polish army. These days we saw grass growing between the buildings and tall trees here and there. It could have been described as a grim sort of campus. In 1942 they held an unimaginable 20,000 prisoners. Each person got far less space than a farmer provides a pig.
Several countries have displays inside the various buildings with photos and artwork.
They found these even though the Germans spent three months destroying evidence including burning down 30 warehouses full of the personal items of the prisoners. There was also a display of bales of cloth made from human hair. We also saw the wall of death. In addition to gassing the prisoners to kill them, the SS simply stood many of them in front off the wall of death and shot them. They shot so many that they had to build an especially thick wall for the purpose.