One of my favorite places to sit and people watch is right by the Russian embassy just next to the Brandenburg Gate. If ANYONE is sitting or standing in one place more than 15 or 20 minutes just watching (not eating lunch or not chatting with someone) the Polizei WILL come ask you what you’re doing and for your ID. They ask ANYONE. They don’t say much else once they check. It’s just to let you know they’re aware of you.