There is a place east downtown right in between all the touristical points of interest where the Berliners are almost under themselves: Its the christmas market directly by the Palast der Republik. This one is a nice mixture of christmas market and fair with rides and merry-go-rounds. But in opposite to the usual fairs, you won’t hear any techno at the rides but christmas music all over the plaza. When I walked there I noticed that there is hardly any other place downtown where I heard so many people talking in the berlin dialect as on this market. Maybe it is because tourists think “ah, its just a normal fair like the one in our town” when they see the ferris wheel etc from far away? Who knows, but if you wanna hear how Berliners talk you got chances to listen to them at that place