The “official” topographic map has a little strip that indicates the slope, which is nice: It doesnt show the underwater part either, so it’s not cheating apparently. I couldn’t find a direct link for it https://www.geoportal.nrw.de/application-geoviewer/start/index.php

Hello, thanks for the comments. So the dam wasn’t missing after all! To tell the truth, I don’t know what the best practice for dams is (that’s exactly why I looked at this particular dam: I have been adding some dams in Afghanistan and I was searching for existing examples for guidance):

• So, should there be a separate line (like way/105671446) that can’t be found because it is in the same place as the shoreline?

• or, should it be integrated in the shoreline (like I it did with way way/353892535, and messed on my first try, you’re right MarkusHD ), so it’s not a separate feature in its own right anymore?

Maybe the best thing would be to model the dam as an area, but that is difficult and would require more research (as the only consistently visible thing is the crest, and one can’t know the exact extent of the building below water without looking at plans).