OK, in terms of "facial features", I was planning to superimpose a female face onto this, but couldn't fid a pic of a gal with the correct head shape..... but it does kinda look like a head could go there, couldn't it?

Also, kinda looks like one of those illusions that you can't tell if it goes inwards or is coming out.

.... it goes inward, if ya can't tell. Wa spart of a large diorama for the Warsaw Uprising Museum, of the sewer system.