Grand Prismatic Spring
This is the largest hot spring in Yellowstone and third largest in the world. The neon colors seem to be unnatural as if someone poured in buckets of vivid paint in concentric circles. The colors are indeed natural caused by different types of heat-loving bacteria. The center which is a clear, aquamarine blue is about 189 degrees Fahrenheit, too hot for most organisms to inhabit. As the water bubbles out from the center the water cools, forming rings that each have a different albeit mostly constant temperature. It is within each ring where each type of bacteria live according to what temperature they like the best. The colors you see are the bacteria reflecting different wavelengths of the visible spectrum. Although you certainly cannot swim in this spring or any hot spring in Yellowstone Park it is free to visit and simply gaze upon.