Before I got to Berlin, Steffi connected me with the Unicycle Berlin group, and one of the locals (Lena) posted about a informal mountain bike race happening in the Müggleberg forest shortly after my arrival. It was a fun format: no timing, just a figure-8 loop through the forest, winners counted by number of laps. You got a token when you passed the start/finish line to count your laps.
The course was mostly non-technical forest road and singletrack, with two or three technical, rooty downhills, and two quite steep uphills which might have been rideable on a casual ride, but wound up being walks during the race.
There were three unis (me, Lena, and Finn), and maybe 12 bikes. Finn went out ahead of me, but it was a tiring course and I caught him before the third lap when he got tired. The start/finish line was near the top of the hill, so after the race we got to ride the Müggelberg North Shore structures on the way down. They gave a fairly tame park (114.7m elevation, highest real hill in Berlin) some spice.
Some currywurst and beer down by the lake, and the day was complete!