Years ago, while stationed in Geneva, I helped a buddy living just over the border in Lully, Haute-Savoie (as in the French Alps) build an indoor snake pit for his big pythons in his basement... I **** you not!
First, we wrapped two layers of cheap thin fiberglass thermal insulation around the sides and over the bottom of a giant plastic horse trough; securing each layer with duct tape. Second, we sprayed foam insulation over it. Third, spray painted it with gray and black Krylon… it looked just like rock when we were finished.
It is very important to insulate the bottom; if you are clever and careful you can keep it very flat and level… we had to use more duct tape to mold it correctly and when the foam was nearly dry after spraying we flipped it over unto cut-opened refrigerator boxes, used a level, and pressed down on the sides that were not even until we are pretty much square and level all the way around. It took us a Sunday afternoon to complete. We literally sprayed painted over the foam as soon as we leveled the bottom and it was dry to the touch; maybe should have waited a little bit longer but it worked.
Similar Products That We Used:
Insulation:
http://images.lowes.com/general/f/fibrgls_roll.jpg
Spray Foam Insulation:
http://www.dap.com/product_details.aspx?product_id=10
Krylon Waterproof Spray Paint:
http://www.krylon.com/products/fusion_for_plastic/
***Beware! It can be messy and toxic when applying so do it outside in the open air. Good luck!***