The Purple Loop Trail at Hartwood Acres Park in Indiana Township, Pennsylvania is a moderate and really nice 2.3-mile trail through the southeast section of the park with a lookout point.
The trailhead can be found in two locations along Hartwood Acres Drive - both visible from the road next to the parking area. Head to the western trailhead to follow the trail in the same direction of this trek.
Lookout Point: Just after hiking the switchbacks during the first 1.5 miles of the hike, you'll reach a lookout point at the top of the natural gas line around mile 1.7 (while following the same route here). This lookout point faces southeast from Hartwood Acres Park looking down toward Saxonburg Blvd and the surrounding neighborhoods.
When you get to the southeastern part of the loop (in this GPS data), you can keep right or keep left to avoid looping depending on which direction you're traveling. That section was a bit confusing on the trail.
Parking: You can find parking at the main lot for the Hartwood Acres Mansion.