Aufeis is an ice feature where a spring that runs year round is forced through a narrow area between two steep hillslopes. The water is forced up through frozen ice and out before freezing. The result is that ice can build up at at large depths from one small spring. The aufeis was 15 feet high in places. When it melts out during the spring, melting water forms unbelievably beautiful caves and grottos along and through the stream flowing through the ice. I think we saw every shade of blues, whites, grays and even some purples.