The Great Chain, as the rotating city was called, lined a circular opening, like an iris, in the middle of the Eye. To either side of it, the Eye tapered to a point. One of those points was always aimed toward the center of Earth and the other was always aimed away from it. A cable, or rather a redundant, self-healing network of them, emerged from each of those two points. The inner one hung almost all the way down to the Earth’s surface, where a thing called Cradle dangled from it. The outer cable stretched for some distance beyond the habitat ring and terminated in the Big Rock, which served as a counterweight. By adjusting the length of the latter cable it was possible to move the whole construct’s center of gravity closer to or farther away from Earth, causing it to speed up or slow down in its orbit relative to the habitats in the ring. Thus it could sweep around like the hand of a clock, passing around each habitat along the way, or pausing for a time as needed. And when it was encircling a particular habitat it could easily exchange people and goods with it, via flivvers, or cargo shuttles, or swarms of nats, or mechanical contraptions that could snake out like tentacles.