Düsseldorf Airport is the largest and primary airport for the Rhine-Ruhr metropolitan region – the largest metropolitan region in Germany and among the largest metropolitan areas of the world.[5] The airport is located in Düsseldorf-Lohausen. The largest nearby business centres are Düsseldorf and Essen; other cities within a 20-kilometre (12 mi) radius are Duisburg, Krefeld, Mülheim an der Ruhr, Neuss, and Wuppertal. The airport extends over a compact 6.13 square kilometres (2.37 sq mi) of land – small in comparison to airports of a similar capacity, but also a reason for Düsseldorf being known as an airport of short distances.[clarification needed] The airport has more than 18,200 employees.