Find the open-air ampitheatre built in 1935 by the Nazis using forced labor. It's somewhat overgrown with weeds and a little derelict. Walking through the ampitheatre and up the steps is a little spooky. If you stand on the stage, and someone else stands at the top you can speak to each other without raising your voices, because the acoustics are so good. At the top of the steps, you are actually at the highest point of the hill.
So while Heidelberg remains largely intact since the atrocities of the World Wars, it still is marked with the "Heiligenberg Thingstätte." I've *heard* that on the rare occasion the ampitheatre is used for entertainment, but in the wintertime it is mostly reserved for sledding enthusiasts. Be sure to bring your inhaler if you plan on walking to it.
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