I found it! NB recommended this place on Hauptstraße from his year spent in Heidelberg. Ein kugel each of hazelnut and ricotta gelato — unusual flavors, and incredibly rich and delicious!
You won’t find “ice cream” shops in Germany [or really anywhere in Europe, now that I think back on it], only Italian gelato with exotic choices like blood orange, stracciatella [similar to vanilla chocolate chip], or even Vegemite [in Australia — it was disgusting!]. It’s displayed in mounds that look almost fake, the top artfully swooped and shiny, often with some sort of garnish sprinkled over and a card stuck in the front with the name and a cutesy drawing depicting the flavor. The cones are extra tall and skinny, the tiny scoop perched precariously like that game of landing a ball on a string into a cup. Lick fast, or it might topple off!