Looking down into the canyon toward Lower Falls, the first thing you notice isn’t the falls tumbling from the far horizon. It’s the canyon walls sloping down to the Yellowstone River. Flecked with green, heat and time have turned once brown rhyolite rock into shades of red, bright yellow and burnt orange. Shaped by 160,000 years of wind, water and hydrothermal activity, the canyon’s skirt of color drops toward the thunderous mint green river below. It is several minutes before I begin to take in the 308 foot falls flowing over volcanic rock.