Take a look at the DGM1 

https://bb-viewer.geobasis-bb.de/?layerIDs=237,9001,9000,133,159&visibility=true,true,true,true,true&transparency=0,0,0,0,0&center=406077.9866696766,5738867.959106498&zoomlevel=9

Do you have an alternative? 

natural=cliff is the best possible... 