"The evolution of the Auschwitz concentration camp is captured in the hundreds of architectural plans the Germans forgot to destory and the Poles and the Soviets preserved the the archives in Oswiecim and Moscow. A unique historical source, these materials are part of the archive of the Zentralbauleitung der Waffen SS und Polizei, Auschwitz O/S (Central Building Authority of the Waffen SS and the Police, Auschwitz in Upper Silesia). For while the Germans burned the archives of the camp Kommandantur prior to their evacuation from Auschwitz in January 1945, and Allied bombs inadvertently helped them accomplish the same task as SS headquarters in Berlin, the archive of the construction office, some three hundred yards away from the Kommandantur, was overlooked and remained intact. There is no similarly complete archive from any other concentration camp, and none of the administratively less complex Operation Reinhard death camps under the control of Odilo Globocnik (Belzec, Sobibor, Treblinka) generated such documents."
"... Drawings in the Building Office archive illuminate the step-by-step transformation of the crematoria from an incineration system for the efficient disposal of corpses to a lethal installation for the murder of live human beings - and then for the burning of their corpses. The plans for the so-called new crematorium, designed for Auschwitz I but erected in Birkenau, clearly illustrate this evolution. Originally (plates 14 and 15) the architectural style and the solidity of the material fit the vernacular of the main camp. As conceived in the autumn of 1941, this was to be a crematorium to accommodate the mortality of the concentration camp at Auschwitz and the prisoner-of-war camp at Birkenau."
(Dwork & Van Pelt, between 320-21)