The Strip District section of the Three Rivers Heritage Trail is an easy 3 mile out-and-back hike that leads from 27th street to the Rachel Carson Bridge and the Downtown TRHT and Point State Park section and back. The trail has a few main view points - you can see Herrs Island in the Allegheny River, the Rachel Carson Bridge, Andy Warhol Bridge, Roberto Clemente Bridge, Downtown Pittsburgh, and the convention center right on the edge of the trail.
Parking can be found for free at the end of 24th street - there are 2 or 3 public parking spaces; however, there's plenty of parking found in/around the Strip District. Parking over by the 27th Street entrance appears to be permit-only parking on the street, but I did not confirm that.
Note: As of early February 2018, there's still construction going on between 15th and 21st street and the trail is closed between these streets. The GPS data provided includes the detour portion of the trail that heads over to Smallman Street and then back to the trail. This construction has been going on since Spring 2017.