The Festung Hohensalzburg (Salburg High Fortress) is undergoing some renovation as you can see.  This seems to be the current rage in Europe -- all the old castles and fortresses are being refurbished: Läcko in Sweden, Salzburg, Schloss Neuschwanstein... The aim seems to be to restore them to as nearly-original condition as possible and consistent with a tourist attraction.
That's fine with me...  There's nothing I like better than seeing a historical site the way it would have been seen when it was new.  I just wish they'd get them all finished.