In search of Berlin's northernmost point

[lethargic_man]

I was browsing Google Maps the other day, looking for new places to go on the cycle rides that have replaced commuting as my form of exercise whilst I am working for home, and noticed a peculiar finger of land pointing northeast, at the northernmost point of the city-state of Berlin:

Only a hundred or so metres wide, it narrows to half of that at its northernmost point. Aside from wondering why on earth the boundary did that,^* I thought: I have to go there and see what it looks like, at Berlin's northernmost point.

* Almost certainly due to the interchange of land ownership by the nobility (and minor royalties) during the Middle Ages (due to buying, selling, and marriages) that led to the internal divisions of pre-1945 Germany having such a fractal complexity; my guess is that the boundaries of Buch were determined by which lord owned which land at some point, and then in 1920 the entirety of Buch was glommed onto Berlin.

So I did. It was a substantial bike ride—a full hour less loose change from home—and what I was surprised to find was that although the end of the finger of land ran alongside a path, the northwest side ran along no obvious property boundary, but rather through the middle of a field:

(Berlin coloured by me in purple, Brandenburg in natural colours; boundary demarcation approximate.)

There was also no indication whatsoever that this marked a state boundary.