Watch the sunlight sparkling on the water as it tumbles over Gossnitz Waterfall. Keep a lookout for pretty rainbows in the mist.
You're spoiled for sightseeing choice when in Heiligenblut. Gossnitz Waterfall is a good place to kick off here, but there are numerous other interesting sights to experience. Grossglockner, Grossglockner-Grossvenediger, and Pasterze Glacier are near the cascade of water and will fill in your day nicely.