Entrance is free in general, but visitor numbers are regulated by a ticket system. Be aware that because of the large numbers of visitors, entry to the Auschwitz I site is done exclusively on a paid guided (yet unfortunately rather rushed) tour between 10:00 to 15:00 during the period from 1 April to 31 October. You can visit the site on your own (which is highly recommended, as visitors can go at their own pace, see what they want to see, and have a much more meaningful experience) if you arrive before 10:00 (better 8:00-9:00) or after 15:00 (depending on the season and day of week). This is recommended if you're staying nearby in Katowice or Kraków and don't have your own car, with some trains from Kraków and Katowice Główny arriving between 8-10. Guided tours cost 45PLN (discounted price for students up to 24 years of age is 30PLN). Students with an ISIC card are granted free entrance during tour hours. If you're a small group (~4 or less), it's not too hard to buy tickets on site (but depending on the season, you might have to wait depending on availability), but larger groups should book tickets in advance.
Of those who received numbers at Auschwitz-Birkenau, only 65,000 survived. It is estimated that only about 200,000 people who passed through the Auschwitz camps survived. Michael Bornstein was one of the lucky ones. Decades after the war, he learned from Auschwitz documents kept in Israel that he had survived because he was sick and the Nazis left him behind when they evacuated the camp. He said that he was one of only 52 children under the age of eight who lived.
In 1942, after the death of Armaments Minister Fritz Todt, Hitler appointed Albert Speer as his replacement. Wartime rationing of consumer goods led to an increase in personal savings, funds which were in turn lent to the government to support the war effort. By 1944, the war was consuming 75 percent of Germany's gross domestic product, compared to 60 percent in the Soviet Union and 55 percent in Britain. Speer improved production by centralising planning and control, reducing production of consumer goods, and using forced labour and slavery. The wartime economy eventually relied heavily upon the large-scale employment of slave labour. Germany imported and enslaved some 12 million people from 20 European countries to work in factories and on farms. Approximately 75 percent were Eastern European. Many were casualties of Allied bombing, as they received poor air raid protection. Poor living conditions led to high rates of sickness, injury, and death, as well as sabotage and criminal activity. The wartime economy also relied upon large-scale robbery, initially through the state seizing the property of Jewish citizens and later by plundering the resources of occupied territories.
Large segments of the Nazi Party, particularly among the members of the Sturmabteilung (SA), were committed to the party's official socialist, revolutionary and anti-capitalist positions and expected both a social and an economic revolution when the party gained power in 1933. In the period immediately before the Nazi seizure of power, there were even Social Democrats and Communists who switched sides and became known as "Beefsteak Nazis": brown on the outside and red inside. The leader of the SA, Ernst Röhm, pushed for a "second revolution" (the "first revolution" being the Nazis' seizure of power) that would enact socialist policies. Furthermore, Röhm desired that the SA absorb the much smaller German Army into its ranks under his leadership. Once the Nazis achieved power, Röhm's SA was directed by Hitler to violently suppress the parties of the left, but they also began attacks against individuals deemed to be associated with conservative reaction. Hitler saw Röhm's independent actions as violating and possibly threatening his leadership, as well as jeopardising the regime by alienating the conservative President Paul von Hindenburg and the conservative-oriented German Army. This resulted in Hitler purging Röhm and other radical members of the SA in 1934, in what came to be known as the Night of the Long Knives.
At Auschwitz I, the majority of the complex has remained intact. The architecture of the camp consisted mostly of pre-existing buildings converted by the Nazis to serve new functions. The preserved architecture, spaces and layout still recall the historical functions of the individual elements in their entirety. The interiors of some of the buildings have been modified to adapt them to commemorative purposes, but the external façades of these buildings remain unchanged.