By airship over the biggest city I've ever seen

For my last big excursion I went up — gently, in a blimp. The Solivagant has airships the way we have buses, and one of them does a slow tourist loop over Calenture, which is the largest of the cities and, I am now fairly sure, the largest anything I will ever see with my own eyes.

The gondola is all big windows and unhurried hosts handing round warm drinks, and the whole thing just drifts — no rush, nowhere to be. And below you: a city with no edge. Towers and terraces and green roofs and water threading between them, lantern-warm even in daylight, going on, and on, and on. On Earth a city ends at a coast or a curve. This one doesn't end; the world is flat, so it simply fades — sharp beneath you, then soft, then a golden haze, all the way out to a far rim of sky-light that marks where the sun's edge leaks in from behind the world.

I kept waiting for the horizon to do the normal horizon thing and drop away, and it kept not doing it, and eventually I gave up and just pressed my face to the glass like a kid. The hosts found this delightful. They find most things delightful. Best ride of the trip, and the quietest — nine billion people somewhere below and up there it was just the hum of the envelope and a lot of contented silence. Go at "dusk," when the sun-rim turns everything to honey.