The correct answer is Warsaw. The Warsaw ghetto in Poland had the exact numbers that you said which means that there were more than 7 people per room. It was overcrowded and the people were not allowed to leave ever, and great monstrosities were committed to them during and after the ghetto time.
The largest Nazi ghetto—the ghetto—was located in , and held around 400,000 prisoners within an area of 1.3 square miles. NextReset