A Superhero Spot is a location (usually in the real world) where significant damage has been done to the terrain or surrounding buildings walls or pavement with no apparent explaination. At this point it is safe to assume that some sort of Superhero battle had occurred and thus created the massive damage.

Superhero Spot is also a ["Swami"] card:

http://www.splitreflection.com/paulgunn/swami/SuperheroSpot.jpg