what did the prisoners first see when thay arrived in Birkenua?

When the train arrives at Birkenau/Auschwitz, the prisoners see the flaming chimney that Madame Schaechter had prophesied.

His description, "flames gushing out of a tall chimney into the black sky" and that he could smell "an abominable odour floating in the air." "We had arrived -- at Birkenau, reception centre for Auschwitz."