Starting from Light 8 in Gatlinburg, turn onto Historic Nature Trail / Airport Road. At 0.7 miles, veer right onto Cherokee Orchard Road, upon which you will enter into Great Smoky Mountain National Park. After driving another 2.2 miles, you'll enter the one-way Cherokee Orchard Loop. Drive 0.9 miles on the loop before turning right onto the Roaring Fork Motor Nature Trail. The parking lot for the trail to Grotto Falls will be on the left side of the road after driving roughly 1.6 miles on this one-way loop. The trailhead is just beyond the parking lot on the opposite side of the road. Because of the extreme popularity of this trail, there are additional parking spaces beyond the trailhead. Your best bet is to get there early during the peak visitor season.