This image, of an apparently large domed room in the Cave of the Mounds, shows significant color streaking in the stone itself, instead of simple staining on the surface. To the far left, up on the ledge, are two dark formations styled Black Knights.
The description states:
Rare ribbons in stone with black and white stripes showing twin Black Knights at left. Cave of the Mounds, Blue Mounds, Wis.
Unfortunately, there is no way to determine the scale of the picture, so it is not clear if the room is very large, or only slightly higer than human scale or not.
This photo like the others shown in this series, dates from the 1940s.