This is quite an awesome find.
Frank over at "The Real Rittersberg" was inspired by seeing my location tour videos a few years back on youtube and decided to visit some of the locations as well.
He's done an awesome website (something I've never gotten around to doing, so thanks Frank for putting an awesome resource together for fellow GK fans!!!) and you can see it here :
As you can see - he found the real St George's Church interior which is located in Marburg.
Fantastic work and I suggest if you are a fan of the stuff I've done, that you check this site out for more pictures and details about some of the locations in Gabriel Knight 2.
Awesome work Frank!!!