And probably it has to do with the specific light in the Pantheon too. I've checked all my photos from this location, and most of them have this effect. It might be caused by the light coming from two sources: the large front door opening as well as the hole in the roof... See also the attached example.,...
It only needs a little tweeking to get the HDR result, I guess!
Just look at the shadows from their bodies: the light is coming from 80 degrees above, although their fronts are completely lit by the light from the front door.... I think this is the most plausible explanation of the strange effect in these photos...