Gotcha!
Currently it's Battery Örlandet museum, near Trondheim, but the turret isn't from Ratte, it's Caesar turret from Gniesenau with three 280's. Still, the turret should look the same
MKB Örlandet
I'll be damned, I found it on Google Maps!
Austråt Fort
EDIT: And another pics!
MKB_Oerlandet