We completed the new 'rubble helix' in Garden Hill Ontario this September 2011 just a week and a half ago. The twisting columns (all dry laid) were constructed using a very nice Upper Canada Stone 'chocolate limestone' material ( proper name is Highland Dry Wall Stone). It stands over twelve feet high and winds up rotating around a central axis. The large 'wrung stones' were brought in from a quarry near Buckhorn Ontario This helix is built on a floating concrete pad. It is amazingly sturdy.
If you haven't already, check out The three helixes. for more details about the original design ideas and Working our way up the rubble helix to read about the building process.
It seems since building this structure, thinking with my hands just got a whole lot more twisted!