Melt water flowing on the surface of the Pasterze Glacier. From the parking lot on Franz Josephs Hohe one can walk down to the glacier in about half an hour. (The first 3rd of the trail can be skipped by taking the Gletscher Bahn, which was built in 1960's, and used to take tourist to the edge of the glacier.) It is pretty safe to walk on the first few hundred meters of the glacier.