The whole model.
Remember that place where Frodo gets stuck?
This is the "bottom of the mouth" of the cave that shelob lives in. It has been worn smooth by her very large abdomen.
That little hole that frodo crawls through. Shelob can't make it through.
The stairs leading to Cirith Ungol.
Make Gollum jump on Frodo!
Orcs run down the steps.
Shelob in her lair.