The Official Narrative
The Jews, who were selected for gassing, walked down the steps into the undressing room in Krema II or Krema III; frequently, one of the inmate orchestras would be playing classical music, which the victims could hear. The place where the orchestra played was southeast of the Krema III building; the location was outside the barbed wire enclosure around Krema III, and right next to the soccer field. This was the location where concerts were held for the prisoners who worked while the prisoners, who had not been selected to work, were gassed. The victims were told that they were going to take a shower, after which they would have a nice hot meal. They took off all their clothing, thinking that they were going to take a shower, and then proceeded to the end of the long undressing room where there was a door into a Vorraum (vestibule). source
Remains of Leichenkeller II, Birkenau
Movie depiction of people descending into L2 Krema II
Model depiction of lines of people at L2 Krema III
There are no known photos of people queued up walking down the steps of Leichenkeller II, in either Krema II or III. All that is ever shown are the disembarkation off the trains. Considering the number of alleged victims and the domination of Allied air space over Poland it would have been inevitable that there would be at least one genuine photo depicting the alleged scenario.