In context of overlay "Bike paths" – Blauer Weg (Track / Land-Access Road) – https://osm.org/way/22823846 via StreetComplete_ee 57.0:

barrier=retaining_wall,material=stone entlang des gesamten Weges hangaufwärts (rechts).

Attached photo(s):
https://westnordost.de/p/206663.jpg