Great Sand Dunes National Park is known for it's beautiful sand dunes of course. But for those in the know, it's the seasonal river that brings us back here every year at the end of May/beginning of June! On this trip, the seasonal river was fairly low, but still definitely flowing, and in areas it was ankle deep even! The kids (and adults) all immediately became structural engineers and started building dams and diversions to make the water flow where they wanted it to go. My youngest went off by herself and found a quiet island of sand to sit on and build a sand castle, while the river flowed by on either side.