London

They were flying low, and beneath them stretched the same featureless, rut-  scarred plain that they had been passing over for days. To the south, a whitish smear of mist hung over the Rustwater Marshes and the Sea of Khazak, but that  was not what Tom had woken her for. Ahead, rising like mountains into a murk of  their own smoke, stood more Traction Cities than Wren had yet seen in her life.  Lighted windows and furnace vents shone like jewels in the predawn dark. Towns  and cities that Wren would once have thought impressive were rolling to and fro,  but they were dwarfed by the colossal armored ziggurats at the eastern edge of the  cluster, ziggurats whose ten or fifteen tiers of homes and factories rose from base plates a mile across, all armored like medieval knights and prickly with guns and  the mooring gantries of aerial warships. The Jenny Haniver had arrived at the line that marked the easternmost boundary of Municipal Darwinism. She was flying  into one of the great city parks of the Traktionstadtsgesellschaft.

Chapter 8: One the Line, A Darkling Plain, pg 67/492