The Hot Wheels Arch
This was an original idea of mine back in 2004 that was considered for the focus of a professional walling demonstration at Canada's largest garden and flower festival show in 2005 - Two parallel walls joined by a spiral arch.
I photoshopped a plasticine model for the 'looping wall' idea (as it was first called) and planned how we were going make it. Cleverly, the cope stones going along the top of the wall became voussoirs as they went round the loop.
While we never got around to building it at Canada Blooms , a month before the show the 'hot-wheels' loop (as it came to be known) ended up being built by students of mine during a two-day workshop that was held at Landscape Ontario near Milton, Ontario, Canada, back in February 2005. We used a 16 inch diameter sono tube supported through its length by two 4x4s held at their ends with step ladders.