The goal was to turn a 30' x 40' room into a cave...

inexpensively.

#1 Answer - Brown Paper

We got a lot of brown paper donated. Crumpled it up and covered the walls with it.

We then spray painted the paper with black and gray.

To add interest, we used some plastic material for basement sub flooring. (Although we got some feedback that says this looks like Lego blocks. Hmm... maybe another theme...)

To conserve paper, we used some black fabric we already had to make an opening deeper into the cave on one wall. We used crumpled-but-not-so-textured paper on a wall and drew "cave paintings" on another wall. The "paintings" are based on the artwork of Annie Vallotton. We used sidewalk chalk for the drawings but they're hard to see. I'd recommend oil pastels for more vibrant color.

For the ceiling, we used more brown paper torn into stalactites.

Other touches included hanging bllack fabric from the door,  a huge rock (made out of pink foam for our Easter play, and more brown paper on the puppet stage.

This is what it looked like before we added the lights:

Picture 1, Picture 2,  Picture 3, Picture4, Picture 5, Picture 6, Picture 7

And here is an idea of what it looks like with the special effects lights on.

Picture 1, Picture 2

What we haven't added yet are lanterns, bats, and stalagmites (orange cones covered in more brown paper).

The paper, paint, lanterns and bats were donated. The black fabric, lights, sidewalk chalk, and large foam rock we had on hand. We paid aout $30 for the lego-like stuff and that was our only expense. Goal Achieved!