Here I am at the King's Lake (I can't spell it in German, but that is the translation). It is blue-green and one of the most incredible vistas I've ever seen personally. Yes, the various Austrian/Hungarian kings would use the Chateau (castle really) and the lake for their summer and sometimes winter retreats. Now it is a museum and National Forest area.
Next, a photo outside the Von Trapp's family mansion. It was used for filming The Sound of Music. If you remember the scene where Maria and the children fall into the lake from their boat, this is the lake and if you look closely, you can see the patio area which leads down into the lake, where they all stepped out. This place is now a private (no trespassing please!) retreat and conference center owned by... Harvard University (how random). Now look to the left of this photo; there is the fortress which overlooks Salzburg and this is the back view of it, about 2 miles away from the Von Trapp's family home. Apparently the FRONT of the Von Trapp mansion was not impressive enough, so they used another building/place. But Hollywood loved that the family home is located on this lake and has the view it does. Patio scenes and dancing scenes were also filmed here for the movie.