Every 560 miles or so, Heaven’s River had a mountain range circling the inside of the habitat. We hadn’t understood the significance of that distance in the initial investigation, but it was obvious now that it was one "day" length for the artificial sun. The mountains, and that baffle Will had told me about, would help to keep the inhabitants from seeing a sun from the neighboring segment by providing a visual break. The circular ranges also provided anchoring points for thin spokes that ran up to the central shaft. No doubt there were power conduits and access tubes along those spokes as well. Maybe even elevators for access.