Due to being partly surrounded by a big wall until 30 years ago and being governed by its own state legislature, Berlin's urban sprawl is still pretty limited a

Due to being partly surrounded by a big wall until 30 years ago and being governed by its own state legislature, Berlin's urban sprawl is still pretty limited and land is aplenty in the surrounding state called "Brandenburg". So it's much cheaper to buy land there compared to (South)Western German areas.