Wonderful public park in an historic location at the confluence of the Mon, Allegheny, and Ohio rivers. The centerpiece of the park is the well known fountain, plus the remains of Fort Pitt and Fort Duquesne. There's the old Fort Pitt Blockhouse from 1764, which is the oldest remaining building in Western Pennsylvania.
The park is the site of the Venture Outdoors Festival, a free celebration each year of outdoor activities, as well as the Three Rivers Arts Festival and the Three Rivers Regatta.
It's a welcome break from downtown, and a chance to walk around, view the boats and the rivers and relax. Definitely bring a frisbee.
Near the fountain is a marker that indicates the end of a 350 recreational trail that begins in Washington, D.C.