Cold water geyser, up to 60 meters high. Also nice to look at from the other side of the Rhine near Leutesdorf. Simply drive up towards the blackbeer tavern and wait at the Edmunds hut until the ship has docked. 15 minutes later you can see the geyser.
Be sure to visit the Geysir Center before seeing the geyser in person – very interesting and educational. At the Geysir Center, be sure to take the elevator down to the "depths of the earth" – not for the faint of heart ;-)