There's a route in my neighborhood I mapped out some time ago which has always proven to be an excellent workout.
It's just a bit over five miles, doorstep to doorstep, and mostly rolling hills - with one or two that are (at least for me) the kind that turns my entire body into an sorry, oxygen-starved slug of lead.
This evening I graduated to a not-quite-as-sorry, slighty more oxygenated chunk of aluminum.
Next up.......foam core? Balsa wood? Perhaps!