The wall was built using some unwanted Cavity Blocks I acquired from a friend. Each block was cut at an angle so the wall would be circular. There was a delay in starting this stage because of finding a door, and hence getting a frame made to fit the door. The wood is setup to match the frame.
I checked each block to make sure it was level and equidistant from the centre so the wall remained circular all the way up. Quite an interesting problem, but simple in the end.
In the next image you can see my levelling system using blocks in the centre and a bit of 2x1 wood with a level taped onto it. The point of the 2x1 wood was used as the outside of the wall for each block. The door frame is in position, and the Plywood Ring on top of the wall.
