Ich hab mal bei http://definetz.online/defikataster-hp geguckt, und die erwähnen, dass der im rail&fresh-WC sei. Da hatte ich damals nicht geguckt, das hole ich mal nach, wenn ich wieder in Heilbronn bin.

I considered all three options but I found none of them suitable.
For completeness, here is the picture that was attached to the note: https://westnordost.de/p/147692.jpg
You can see that the steps are solid blocks of sandstone, not sett, not paving stones or cobblestones. In Karlsruhe, there are lots of buildings made of sandstone, and often their stairways are made like in the picture.