The capital of Germany, Berlin, is usually not associated with Low German. The Berlin dialect is spoken here, a language that is clearly not Low German.
In fact, Berlin was a Low German city starting with the German settlement of the region in the 13th century. City documents were written in Low German until the 16th century. After that, High German prevailed at the Elector's court in Brandenburg and later at the Prussian royal court. The High German court language, until then only a written language, spread as a spoken language in the city in the 17th and 18th centuries and thus formed a High German island within the Low German Brandenburg dialects all around.
When Georg Wenker recorded the German dialects in the form of maps around 1880, Berlin High German had already spread further into today's suburbs, but the Low German dialect was still widespread in places like Staaken, Zehlendorf, Marienfelde, Mahlsdorf or Blankenburg.
Low German was now so weakened that it soon disappeared in a wide area around the city. It is hardly documented. There were Low German writers who published in Berlin, such as Max Blum, but these were usually immigrants from other regions and published in their native dialect.
One of the few Berliners who published in Low German was Axel von Demandowski (pseudonym Axel Delmar). His folk piece Der eiserne Heiland from 1912 however was deemed as being full of invented false word forms.
The town's Low German vocabulary is recorded (to a small extent, if it has been handed down at all) in the Dictionary of Brandenburg-Berlin.