A hot spring pool found in Yellowstone National Park, Wyoming, changed color from crystal blue to yellow-green because tourists kept on throwing coins and rocks into it. The pool is known as Morning Glory, and has recently been nicknamed “Fading Glory” due to how much it has changed. Tourists throw in coins and rocks because they hope that good luck will then follow them. The debris stuck in the pool’s vents has slowed down the water’s circulation, dropping the temperature and allowing the proliferation of bacteria that produce the unusual pigmentation.