However, there was one place that gave the game away. The crematorium block was a two storey building. The ovens were on the top floor.
Take a look at the picture below. Bodies were stored in this lower room before being taken by lift to the ovens above.
If you look closely you can see that there are hooks all around the room. Prisoners were executed by being hung from these hooks.
A prisoner would be brought to the room and a noose put around their neck. They would then be lifted up and the rope fastened to a hook. They would then be left to slowly choke to death. They would be able to see the piles of bodies and, perhaps, other prisoners hanging from hooks, also slowly choking to death. The Wikipedia article on Buchenwald contains an estimate that 1,100 people were executed by hanging at the camp.
I wonder if they took Obama into that room.