Standing in each archway along the vertical axis is a metal sculpture of a bird with a humanoid face.

The three "birds" and three windows with horns hanging in them are not symmetrically arrayed as they might be if they depicted three mutually orthogonal vertical orientations.

Presumably, behind the picture's overall point of view, the same landscape continues behind the viewer in the same orientation as we see it through the window opposite.

In order to portray three mutually orthogonal verticalities from the point of view of a third bird, the bird opposite that would have to be rotated 90 degrees, and the window adjacent to the viewer show the naturally oriented landscape behind the hanging horn.

This sculpture first appears in Escher's 1934 lithograph Still Life with Spherical Mirror.