The death camps were built where they were because they were strategically located near transportation routes, especially rail lines, which made it easier to transport large numbers of people to the camps. The Nazis chose remote locations to build the death camps to keep them hidden from the general public and to minimize the chances of escape by the prisoners.
The death camps were constructed to look like railroads and factories to camouflage their true purpose and to avoid suspicion. The Nazis used deceptive language and propaganda to describe the camps as "labor camps" or "resettlement camps" to hide their true nature as places of extermination. They also constructed factories within the camps, where prisoners were forced to work as slave laborers to produce goods for the war effort. By portraying the camps as productive and useful facilities, the Nazis aimed to gain the support of the German population and to avoid international condemnation for their crimes.
In summary, the death camps were built where they were for logistical reasons, and they were designed to look like railroads and factories to deceive the public and to avoid scrutiny by the international community.