Rubble Ridge is a short but challenging little trail. It is an alternate route for the South Loop
Trail, traversing a rocky ridge, rather than skirting it as the South Loop
The trail begins with a smooth section along the base of the ridge, followed by some tight turns, and then a tough little climb punctuated by a short section of rocky footing. The trail then follows the peak of the ridge eastward before winding back west through hardwood trees, up a short climb, then down through twisty cedars, with a sharp left at the end, another rocky section, then smooth sailing back to the South Loop
Note that this is not a natural ridge, but was created by quarrying operations that dumped overburden (the top half-dozen feet of small rocks, dirt, and organic matter) into a long pile. But it's had fifty years to settle into place, and has resulted in a trail that offers some decent climbs and some technical sections.