The new urban municipality of Berlin also called Greater Berlin was created 100 years ago on 1 October 1920 following a groundbreaking administrative reform. This was a centurydefining milestone that transformed Berlin into a world city. The old city of Berlin was merged with 7 other cities 59 rural communities and 27 estate districts. As a result the citys area increased from 66 to 878 square metres its population from 1.9 to 3.9 million people virtually overnight. But Greater Berlin did not