Touching cave formations is prohibited. Formations are easily broken and the oil from your skin permanantly discolors the rock. Smoking, or any use of tobacco, is not permitted. Eating and drinking are not permitted except in the Underground Lunchroom. Throwing coins, food, or other objects in cave pools is forbidden.
Foreign objects ruin the natural appearance of the pools and are difficult to remove.
Also, the chemical reaction between foreign objects, the water, and the rock can leave permanant stains. Photography is permitted when you tour on your own, but not when you accompany a ranger-guided tour. Photographers should not rest tripods or other camera equipment on formations or step off the trails. Strollers are not permitted because parts of the trails are steep and narrow.