Main trails and some bike trails at Jordan Creek Parkway in Whitehall (near Allentown). It has an extensive disc golf course incorporated which would provide enough terrain for an interesting sprint map, perhaps, if we had a base map to work from (and folks to come).
Added: Map link
(if you click the link, the Parks Finder will come up and ask you to accept its waiver; after you accept it'll show the trail network. I think its a valuable service from our county)
Otherwise the main trail is pretty boring even though it goes close to Jordan Creek in places. First part was concrete, then gravel (larger stones), then macadam. On the way back from the far end I explored a dirt trail that headed uphill. There were some side trails to adjacent housing areas, and it eventually plunged fairly steeply back to the main trail not far from the bridge across to the isolated spur where MTBers play.
Bike trails are a mix of dirt without too much else and dirt with roots/rocky/steep/obstacles, etc. I didn't cover all the trails but had with me a map from the Lehigh County Parks and Trails website, which includes most but not all of the newer disc golf trails.
About 80F. Shaded, so I wasn't concerned about not using sunscreen.