because this photo is rendered with only direct illumination, areas that are not the first hit point of a ray of light are completely dark. we can see this is reflected (or not LOL) in the way that much of the photo is very dark because there is no direct light (in the foreground, behind the arches) in the following photos, the photo continues to get brighter as we allow light to bounce into these dark areas; some light hitting the floor/walls/etc will bounce onto the completely black areas in this photo and illuminate them.