In context of overlay "Dinge" – Karte – https://osm.org/node/810367231 via StreetComplete 63.1:

Standort "Hohler Stein" + QR Codes * "Naturschätze Südwestfalens 'Lörmecketal'"; * "Geschichte-hörbar 'Der Hohle Stein'"; * "Dorfrundgang Kallenhardt"

Attached photo(s):
https://streetcomplete.app/p/346126.jpg
https://streetcomplete.app/p/346127.jpg