I am currently in Pittsburgh for a medical student rotation. Its perfect time to be in Pittsburgh, the leaves are changing color and hare turning the city and surrounding forests into rainbows.
Recently I visited McConnell's Mill, which is 45 minutes outside of Pittsburgh. This is a 7 mile trail. To the hike the entire trail you either have to take cars to both ends or hike 14 miles. I decided to hike as far as I could in a half a day. It ended up only being about 6 miles. The trail follows Slippery Rocks River which runs through the park.
I also visited Mount Washington and took the "Incline" tram up. This is an old trolly that takes you up and down the mountain. This is a great adventure for both day and night. If you plan to go at night don't forget to have a bite to eat at one of the restaurants at the top. The views are amazing.
Other than hiking there are plenty of restaurants to try. Check out Shake Shack, Meat and Potatoes, Primanti Brothers, and Big Dog Coffee.