Berlin is Germany's capital and co-extensive with the Land of Berlin, one of the 16 federal states that make up the Federal Republic of Germany. With a population of 3.8 million (2019) (and a million more in "suburbs" like Potsdam across the state line in Brandenburg), Berlin is Germany's biggest city.Berlin is unusual among European capitals in many respects and the four decades of partition—28 years of them being physically separated by a wall—have also left traces. Merely a backwater town in the early 18th century, Berlin grew to be one of the most important and biggest cities in the world by the 1920s, only to lose much of its importance and historic architecture as a result of World War II and German partition.The heart of old Prussia and a focal point of the Cold War, Berlin today is coming into its own again as a cosmopolitan capital of one of Europe's wealthiest nations. "Arm aber sexy" (poor but sexy) as a former mayor would have it, Berlin attracts young people, students and a creative bohème like few other cities in the world. Due to its long history as a cosmopolitan capital (first of Prussia and later of Germany) it has attracted immigrants from all over the world for more than three hundred years now, who continue to leave their own marks on the city.