Rodale Cycling & Fitness Park in Trexlertown, Pa. has a wonderful 3-lane looping track for bicycles, roller blades, and walkers.  There is also a nice nature trail through the woods.   I’ve walked the track many times and it’s 1 mile long on the outer loop and .6 miles on the inner.  Nice and flat, too!  I had my camera along last time and took a few photos along the way, including this one where you can see the repeating lanes of the track … slow walkers on the left, roller blades in the middle, and fast bikes to the right.