One of the homes of Kassel's last prince-Elector, which I think is Royalty-wannabe, but you can only have one King. This guy had four kids with his wife, 13 with his primary mistress, and a dozen more with various others. Prolific. In addition to this place, I believe he had a place "in town" and a small castle up the hill a bit for his primary mistress.
This has been rebuilt since the war, though the left wing as you see it from this view was left standing and is now a museum of sorts.
I see you made it to the town where I spent many a summer as a youngster. From where you took this photo you are within walking distance of where my family lives. Hope you got up the hill to the Hercules...quite the view from up there! :)