Aletsch Arena is a great place to view the golden larch trees, starting around mid October.
This trail starts at Belalp and hikes down to a suspension bridge over the gorge cut by the glacier. Then up a mountain filled with golden larch trees. Then down to the alpine village Riederalp, where you can take a cable car down to the valley and catch a train back to your starting point.
Trail: 11 km • about 4-5 hours • 600m up, 700m down
See trail map
More info on SwissFamilyFun.com.