Within the city limits, Frick Park is great, especially that passes below below Forbes Avenue and further South. Schenley has good casual walking/hiking trails.
Both are highly accessible from most campuses.
Harrison Hills park is also a nice park. It is one of the county parks (like N. Park or Hartwood). It has a really long trail that runs along side the cliffs over the Allegheny River. To hike the full loop takes about 2 hours with good views pretty much the whole time. It is right outside of Natrona Heights. From where you live, you could take 28 North to get there.
- Racoon Creek is great for hiking. Some of the trails can get very water logged after the rain but definitely my favorite for hiking.
- South Park is also very nice and has a pretty good golf course.
- The Montour Trail is obviously not a park but an awesome trail for hiking and biking. The map on the sight will show you many different places to get get on it and there are tons of little trails that spin off the main one.
Don’t forget the Three River Heritage Trail. It’s nowhere near as beautiful as dedicated parks, but it’s great for walking/biking.
For excursions, I recommend Lake Arthur in Moraine State Park. Lots of trails and lake coves.