A nice, gentle 2.5 mile loop around the two beautiful lakes
A reconstructed British fortification from the French and Indian War around 1758. It has the reconstructed fort together with a museum containing artefacts from the period.
An outdoor paradise with hiking, kayaking, white water rafting, and cycling. Definitely worth a day trip (it is about an hour from Greensburg).
One of the most famous Frank Lloyd Wright houses; really close to Ohiopyle for a combined day trip. Other FLW houses nearby are Kentuck Knob and Polymath Park.
A load of hiking trails in the woods, close to Ligonier for exploration and sustenance after!