Near the great white scar formed by the china clay works at Trowlesworthy is a complex of stone rows and cairn circles not unlike those at Ringmoor. From where you park the car, you can see the rows sloping down the hill. Having sight of them makes the incredibly dull hike over to them slightly more palettable. Be careful how you go - you can access the site from either side of the canal, but there is no path so tread very carefully. The ground underfoot almost got me a couple of times! The are a couple of rows here the main one perhaps just less than 100ms long - hard to say as an artificially cut channel now bisects it.
The cairn circle is charming though and despite the fact you're overlooking an industrial landscape, I quite liked it.