4. Brussels, Belgium
Brussels grew from a small rural settlement on the river Senne to become an important city-region in Europe. Since the end of the Second World War, Brussels has been a major centre for international politics and has become the home of numerous international organizations, politicians, diplomats and civil servants. Brussels is the de facto capital of the European Union as it hosts a number of principal EU institutions (the other administrative centres are Luxembourg and Strasbourg). The secretariat of the Benelux and the headquarters of the North Atlantic Treaty Organization (NATO) are also located in Brussels. Today, it is considered an Alpha global city.