The South Loop Trail offers the most spectacular views at Lehigh Portland Trails. Beginning at the Backbone Trail, the singletrack follows an old roadbed past the remains of several farmsteads, of which all that remains are stone foundations and rock fences made from locally-quarried limestone. After passing the farmsteads, the trail skirts the edges of Rubble Ridge, before emerging on the verges of the Lehigh Prairie, where the trail roller-coasters through trees for a couple hundred yards before briefly passing through an open area of tall prairie grass, before rolling through mature cedars and across a rough creek crossing. When the trail runs north, the view opens up to reveal a 100-acre spring-fed lake formed from a limestone quarry hollowed out over 70 years. The trail runs just feet from the edge of 30-foot bluffs as it follows the lake perimeter. There are several places to stop and just take in the view before continuing. After a short section of prairie grass, the trail surface becomes rocky, and the plants take on a southwestern feel, with cactus, yucca, and hardy species that thrive in rocky, marginal soils. After nearly a half mile along the towering and precarious bluffs, the trail drops into a densely wooded area, where it follows the terrain around and down a ridge, before hitting an old quarry haul road that leads back to the Backbone Trail.
The full trail is about 1.7 miles, but there's a shortcut trail in the center that provides a shorter loop option. The South Loop Trail traverses a wide variety of terrain and a diverse array of environments.