In my neverending attempt to be healthier, I tend to park at the back of the grocery store parking lot, increase my veggie intake (while decreasing red meat) and I also sometimes do weird things (if I have to go up a flight of stairs, I might turn around and do it again just for the extra effort). But I don't know why I haven't yet gone to Swallow Cliffs. It's a forest preserve within driving distance of my home and there used to be a big toboggan run. Once they stopped using the toboggan run, the stairs were still there, and they have become a mecca for fitness enthusiasts. People walk up or run up and down the 125 uneven steps over and over, leaving piles of pebbles at the top to keep track of their laps. There's an added challenge in that the steps are not all the same size (when they rebuilt them a few years ago, people demanded that they be rebuilt just as they had been, uneven).
Here's the toboggan run (with the steps beside it) back when it was still open for tobogganing.