Spiral ceiling's free form shape can
only be done with lath and plaster.
Attention is drawn to the octagonal
ceiling.

Top right:

Octagonal ceiling: very well done.
Angles (inside corner) are straight
and well done. These are called "splay"
angles in plastering. The take a long time, but are worth it.

Left:

Upper floor showing the panoramic view.
Even the sills are plaster. Excellent job,
Harry