Here's a site on Nazi architecture that includes images from the 1930s and '40s and the same place today. The real interest here is the "Thingstatte" (scroll down to the Heidelberg section) which was called a "veritable church of the Reich" by Goebbels. It was an open air stadium built to harken back to the ancient pagan gatherings. (Page found via Cylindrical Primate Storage Unit.)