I think there's something to be said for taking in the whole trail including the Pittsburgh urban end. If you take in the historical nature of the area and the ride, you really are travelling through time. Although there aren't any steel mills left in Pittsburgh itself, you can see the remnants of the industry in many places. Riding out of the city into Homestead let's you take in the old smokestacks at the Waterfront, some of the old gantry cranes, the site of the Homestead Strike of 1892, and a view of US Steel's Edgar Thomson Works across the river from the trail. You can take in a sense of the scale of the industry and the impact on the area, both economically and environmentally. Several bridges now carrying the GAP were originally built to carry rail cars of hot steel to rolling mills. Riding out towards Connellsville takes a rider in coal country that produced coke for steel production. It's a fascinating history and in many ways, it's a history of America. Reading up on the history of the area before hitting the trail gives a rider a greater appreciation of it all. By the time you get to Rockwood, you can check out a fossil bed of shells laid down 300 million years ago. I can't think of another trail that has this depth of history!