I have an assortment. I have river rocks, one old heat rock with the cord completely removed, a geode, and one of those table top fountains that is filled in with Great Stuff, with sand grouted and sealed in. I also have wooden "caves" (not in use yet, I want to make sure the little ones are acclimating well) I built a "Castle battlement" in a china cabinet for my handicapable 3 footsie Yardley with Greatstuff, styrofoam, and grout, also sealed in. There are also two Quartz pieces, and lots and lots of ceramic tiles.
Janie.