This is grand geyser. Arguably the best geyser in Yellowstone. It goes off every 7 1/2 - 8 hours, and is a fountain geyser rather then a cone. We waited almost 4 hours for this thing to go. We arrived at the beginning of its predicted time, and it went almost at the end. It was absolutely gorgeous! The show lasts anywhere from 10-15 minutes. The geyser shoots water up almost 200 feet into the air!