If you ever end up going down to Pitts,
you'll need 5 hours to get there.
But if you start out early. There's plenty of time.
It's well worth it.
PPG Aquarium
Pennsylvania Waters Exhibit - a river exhibit that flows along the front of the new building, with waterfalls descending into a pool of North American fish from the region.
Open Ocean Tank - a two-story, 100,000 gallon tank that combines sharks, fish, and simulated coral to resemble a more diverse and complete ecosystem.
Amazon Rainforest Exhibit - a two-story recreation of a flooded Amazon rainforest, including lush plant life, piranhas and huge South American pacu.
Two Oceans- a cold water marine exhibit featuring a uniquely shaped window that allows visitors to view fish swimming above and alongside them.
Stingray Tunnel - a unique educational exhibit where children can crawl through a clear tunnel to view stingrays swimming above and alongside them.
As well as a couple of Reef Aquariums set up by Mike Paletta.
(a local Expert Reef aquarist who's written books as well as worked on coral husbandry and has a couple corals coined after his name. Paletta's blue Acros and Paletta purple porites.)
The Pittsburgh Zoo is one of only six major zoo and aquarium combinations in the United States. Located in Pittsburgh, Pennsylvania's Highland Park, the zoo sits on 77 acres (310,000 m2) of park land where it exhibits over 4,000 animals representing 475 species, over 70 of which are threatened or endangered. The zoo also participates in 64 Species Survival Plans.
(Beats the hell out of NY Zoos.)
Start out early, spend the major portion of the day. Eat out and head back at your leisure in the evening or next day.
But that's just what I'd do.
Just an idea.