Where was the Karnstein Trilogy filmed?

The Karnstein Trilogy has 2 titles (1970 to 1971), filmed at 1 place in 1 country. Wikipedia names 2 more. Every place links to its source.

The productions, in order

Every filming location they used

Each place appears once, even when several titles were filmed there.

Named in Wikipedia's own articles

Places named only in the titles’ Wikipedia articles.