The basement was just a formal way of saying prison cells as this was where all the prisoners or "workers" were kept. Mako had some idea of what to expect from the stories he had heard from Bill, but once he made his way down to the basement after almost getting lost two times, he held his mouth with his hands to stop himself from puking.
The smell that was coming from the entrance to the sleeping area was so horrendous that Mako had to force himself not to vomit right there on the spot. He couldn't believe that this was where all these people were kept as he couldn't imagine being stuck here for life.
It took him a couple of moments to compose himself before he entered the main area. The room was quite massive with no walls and only pillars supporting the entire structure. There were a large number of bunk beds that were lined neatly in rows throughout the room and then there was a massive rebar metal wall shaped like a cell door.