Pilgrimage chapel before the reformation, seculare bad weather shelter afterwards. Similar chapels were often used as quarry for parish church repairs (to rob Peter). Did also serve as lodging for game keepers and shepherds. The last squatter held out till the early 50ties (20th century). Post war housing crunch.
If it was once a pilgrim chapel it will have been subdivided into a public access part and a devotional viewing area. Possibly separated by some kind of trellis work. (Highly conjectural, starting or end point of a 13th century Via Dolerosa.)
'Käppele' is a diminutive of 'chapel'.