A Soft Not-Foam-Filling “What am I?” Quiz

Nikon D4 + Voigtländer 125mm f/2.5 — 1/200 sec, f/5.6, ISO 6400 —
map & image data — nearby photos

Not Foam Filling From a Cheap Pillow

but then, what is it?

It's been a month and a half since my most recent attempt
to confound with a
“What am I?” Quiz, but I fear today's may confound but may
not interest. There's not much to go by. We'll see.

As always, I'll hold replies from public view until I post the answer in a day or three...