Next up in our Geyser Grand Slam was Riverside Geyser, another geyser that we hadn't seen erupt yet. Riverside Geyser is on the bank of the Firehole River and is one of the most predictable geysers in the park. Eruptions are about six hours apart and the prediction time gives a one hour window. Its eruption lasts for twenty minutes and shoots a 75 foot stream of water over the river. Very pretty! If the light is right, you can see rainbows in the spray. Unfortunately the sun was hiding behind the clouds when it erupted, but it was still an awesome sight.