Berlin is the capital and most populous city in Germany, as well as the country's biggest by area. With 3.8 million people, it is the most populous city in the European Union as measured by the population living inside city boundaries. In addition to become one of Germany's sixteen constituent states, Berlin is bordered by the State of Brandenburg and is contiguous with Potsdam, the capital of Brandenburg. In Germany, Berlin's urban area has a population of about 4.5 million people, making it the country's second most populated urban region after the Ruhr. Germany's capital area of Berlin-Brandenburg, with a population of more than six million people, is the third-largest metropolitan region in the country, behind the Rhein-Ruhr and Rhine-Main regions.
Berlin is a global metropolis of culture, politics, media, and science that attracts people from all over the globe. Several high-tech companies and the service sector support an array of creative industries, research institutions, media businesses, and convention sites that make up the city's economy. With a very complicated public transportation system, Berlin acts as a regional centre for aviation and train travel on the European continent. The metropolis is a famous tourism attraction for both locals and visitors. A number of other important businesses exist, including information technology, pharmaceuticals, biomedical engineering, clean technology, biotechnology, construction, and electronics.