yeah, right
Paris: 2,241,346 (2014)
Berlin: 3,562,166 (2014)
"Comparing urban areas in the European Union, Eurostat, the statistical agency of the EU, places Paris (6.5 million people) second behind London (8 million) and ahead of Berlin (3.5 million), based on the 2012 populations of what Eurostat calls "urban audit core cities"." — Wikipedia.
Nested administrative boundaries is a UK speciality (e.g. England, Wales and Scotland are countries within a country).
(4M if we count the Metro area)
It seems like a strong telecommuting infrastructure and culture should be a part of this.
The biggest one in Munich is two intersecting streets, each almost 1km long if you measure generously, and some 50-200m stretches of neighbouring streets.
By property value the area is vast ;)