London is a global city, one of the nerve centers in the field of arts, commerce, education, entertainment, fashion, finance, the media, research, tourism and transport. It is the main financial center of the world and one of the metropolitan areas with the highest GDP. London is also a world cultural capital, the most visited city considering the number of international visits and has the largest airport system in the world according to passenger traffic. In addition, the city's 43 universities make up the largest concentration of higher education centers in Europe.