I think Point State Park is worth checking out. Cool view of the city, rivers, and fountain. I also think Mt Washington is a must. You can park at the bottom, basically across from the Point, and take the Duquesne Incline to the top. Then you can walk as far as you want to get some awesome views of the skyline. If you really want your exercise, you could even use that parking lot for the Incline to visit the Point too. Just have to cross the Fort Pitt Bridge via the sidewalk.

I also think the Strip District would be worth visiting. It’s busier on weekends, but it might still be lively on a weekday. Lots of food vendors, markets, shops, etc. and plenty of souvenir options.

Oakland and the University of Pittsburgh, if you have time. I’m biased but I think the Cathedral of Learning is an architectural masterpiece. You might not be able to do a tour of the nationality rooms because of classes - I’m not sure what the summer schedule is like - but you could still check out the ground floor and maybe even the view from the Honors College floor near the top. Nearby Schenley Park will be bustling with life too. The view of the city from the Overlook is gorgeous and really close to the sports fields, so I love the atmosphere there. Also in Schenley Park is Phipp’s Conservatory if Botanical Gardens are your thing.

There’s too much to do here to fit in 6 hours - basically any single one of our museums could fill that. I steered away from suggesting them in order to provide multiple points of interest that won’t take as long to check out. But if you’re into museums, we’ve got some good ones. My personal favorites are the Carnegie Museum of Natural History and the Heinz History Center.

Hopefully that provided at least a few ideas for ya! Hope you enjoy your visit!