Last fall I spent a month building and installing this double arch in a friend's basement. It is structural, so we had to install the 2 steel I-beam arches on either side of the existing wooden beams and posts. Then we shifted the load to the steel and removed the wood so they had a free swinging space for practicing hanging trapeze acrobatics. Then I welded in the ladder rungs and later installed the second pipe arch.
Him and his wife (the lady in the image) have a dance troup called the Cabiri.
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BTW the room measures 17 feet wide, 21 feet long and 13.5 feet high.