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Concrete Split Octagon Framework

Relatively OCD-Friendly.
NOT a perfect octagon due to the split (for a path) and due to barrier lengths being restricted to integers. But it has one line of bilateral symmetry (though the default door isn't perfectly placed).
Inner wall distance between pillars is 8m exactly. Outer wall distance between pillars is just short of 20m. Distance between inner wall and outer wall is 28m. Wall height is 6m.
The framework was intended to be split into 7 or 8 separate habitats (depending on whether you add spokes from the midpoints or the corners), with doors facing inward to a staff hub in the centre and visitor paths around the outside.
You could just remove the path split and repair the octagon if you intend to path staff in from above or underground.