No construction information was listed in the source material.
Ioun towers range anywhere from 50 to 100 feet in height.
Ioun towers act as arcane signal transmitters, blanketing a 7-mile-radius with a unique magical effect based on the type of ioun stone embedded within it. For example, a tower with a clear spindle ioun stone slotted into it grants all creatures within the area the beneficial effects of a clear spindle ioun stone, which alleviates the need to drink or eat. The GM should adjust or modify other stone effects as appropriate for their campaign.
Ioun Stone Removal A successful DC 40 Use Magic Device check allows a creature to successfully swap out the embedded ioun stone in a tower. Some ioun stones work better in this configuration than others, while some simply do not function in an ioun tower (GM’s discretion).
Pathfinder Adventure Path #126: Beyond the Veiled Past © 2018, Paizo Inc.; Authors: Thurston Hillman, with Robert Brookes, Eleanor Ferron, Crystal Malarsky, and Scott Sharplin.