The Tranquil Trail at Frick Park, Pittsburgh, PA, is an easy 2.6 mile out-and-back hike that leads from the northern section of Frick park (near Reynolds st and Penn ave) down to the southern end of Frick park (near I-376).
There's parking at both ends, but the south end has a large parking lot. The trail is mostly flat with an incline near the northern section. Very populated + lots of dogs.
This is definitely one of the best hiking trails within Pittsburgh and Frick Park.