I first pictured a hillside strewn with building site refuse, bricks, breeze blocks etc. Dug in concrete on a farm track i'm used to, we got a lot of that round here.
I've found myself a trainning circuit, mixture of B-road, farm/forest road and single track with steep climbs, descents, mud, roots, loose surface gravel etc. Not timed myself yet but its a great SS workout.
Should I ever get down Grantham way, I'll have to get you to show me around this circuit of yours