On 1 January 2006, the office of the Hamburg metropolitan region opened, as agreed in a state treaty of cooperation (Staatsvertrag über Zusammenarbeit) between Hamburg, Lower Saxony and Schleswig-Holstein.
In 2005, the Hamburg metropolitan region consisted of the city-state Hamburg, rural districts of Lower Saxony, and districts of Schleswig-Holstein, with more than 800 cities, towns or municipalities. The region covered an area of 19,802 km2 (7,646 sq mi).
The Hamburg Larger Urban Zone (LUZ) as defined by Eurostat's Urban Audit covers an area of 7,303 km² and in 2004 contained 3,134,620 inhabitants (pop. density 429/km²). The Larger Urban Zone covers the Free and Hanseatic city of Hamburg and only the directly bordering districts: