In the woods above Neuviller-la-Roche and Natzviller are the Serva Falls. While not the largest we've covered, they are still sizeable, with the river flowing over rocks a small distance either side of the main fall.
It's a good hiking destination from Rothau or even Schirmeck station, depending on how far you're prepared to walk. I started in Rothau, had lunch by the falls, down the river back to Rothau, and wound up adding a walk in the valley to Schirmeck while waiting for the next train...
A good hike I'd like to do is 2-day, 30-km walk from Rothau up past the falls to Champ du Feu, the highest point in Bas-Rhin, and on to the plains at Barr. But I wouldn't want to do it alone.