So, in the scene where Albion is describing Spire Albion he says it is 10,000 feet tall and 2 miles wide, with 250 habbles, with 236(?) populated. The math seems to work out as the spire being a huge cube, somewhat shorter than it is wide.  That also works out to 40 feet per habble, although it would be a indeterminate amount less depending on how much spire stone is between levels.