Karlsplatz, here seen from top of the church, has always been a problematic spot. It was never pretty. Today it is mostly covered by Ressel-Park, the park in front of the old Building of Vienna’s Technical University. The rest is the crossing of a few big streets, and of course (what you don’t see) the crossing of three Underground lines. It’s the major Underground hub in Vienna.
In recent years, excessive policing has kept drug dealers and consumers off Karlsplatz, but of course the problem was only pushed to other, less prominent place.