In chapter 14, Hannah explains to Shifre and Rivka that whenever Commander Breuer comes to inspect the camp, all the children under fourteen years of age have to disappear. Children under fourteen years of age are not allowed to be in the camp. Hannah tells Shifre and Rivka that therefore, whenever Commander Breuer comes to the camp, all the children must hide "in the midden."
When Hannah tells Shifre and Rivka about the midden, they reply, incredulously, "the garbage dump?" Hannah confirms this. The children are of course a little perturbed at the prospect of hiding amidst piles of rotting and smelly garbage, so they are a little surprised when Hannah tells them that this is where they must hide.
Hannah explains that the midden is the "best hiding place" because the Germans consider it "beneath them" to look there. She says that the Germans know that there are probably children hiding there, but they are happy to pretend that they don't know this if it means they don't have to go there themselves.
In chapter 15, all of the children "race toward the midden heap" when they hear that Commander Breuer is coming to the camp. When they get to the midden, all of the children take off their clothes and dive "naked into the dump." Hannah is described as wading knee-deep "through a mixture of old rags, used bandages, the emptied-out waste of the slop buckets." The midden is, unsurprisingly, described as having a disgusting and "overwhelming" smell, which is far worse even than the already terrible smell of the camp.
Later in chapter 15, the Commander arrives at the camp. He walks through the camp "without giving the dump a glance," seemingly confirming Hannah's theory that the midden is indeed the best place for the children to hide.