Answer:
So they could be transported easily to other places for the final solution.
Step-by-step explanation:
Nazi ideology used traditional Christian antisemitism, which portrayed the Jews as an inferior and destructive race. The purpose of putting Jews in concentration in central locations was to eliminate them from cities and to give German people living space (lebensraum).
Ghettos establish near railroad so that they could be taken to remote areas, away from people eyes and world. Jews shifted to concentration camps, where they were punished and did labour work. These camps were built and operated by Nazi Germany.