London is one of the world's leading cities in the fields of arts, commerce, education, entertainment, fashion, finance, health, media, professional services, research and development, tourism and transportation. It is one of the largest financial centers in the world and has the world's fifth metropolitan area GDP. London is generally regarded as a world cultural capital. It has the world's most visited city as measured by international arrivals and the world's largest city airport system measured by passenger traffic. It is among the world's leading investment destinations and is home to more international retailers and ultra-high net worth individuals. Universities in London are made up of Europe's largest higher education institutes.