Grunewald is a great place for runners as it offers all sorts of different terrain in 22km².
I didn’t pick a specific route here because I think the best way to experience Grunewald is to simply run and see how far you can go. And you can go quite far, running through the thickest forest, over sunny glades and sandy lowlands. Here’s an example of a 16km route (in German).
As you might get lost it’s wise to carry a mini-map with you. My favourite songs while I got lost in Grunewald:
Totally Enormous Extinct Dinosaurs: The Waulking Song
Atmosphere: Get Fly
The Wombats: 1996