Skyholm

In other works, Poul Anderson describes large, spherical faster than light spacecraft capable of waging pitched battles in space with force fields and nuclear missiles. "Captain to all officers and men! Captain to all officers and men! Merseian warcraft sighted! Stand by for hyperdrive! Stand by for combat! Glory to the Emperor!" (Here I quote from memory but that is the sort of thing.) This reads like stirring stuff but Anderson always makes sure that we know what it means when a single sentient being dies.

We can vicariously enjoy faster than light space battles, described with technical precision, first because they are unlikely and secondly because, with humanity, in that period, spread across a vast volume of space, no war can threaten racial survival. Despite the deaths, it all seems like a game: "The Game Of Glory"; The Game Of Empire. Later, in the Commonalty period and on an even vaster interstellar scale, humanity might have left war behind.

I mention large, spherical faster than light spacecraft in order to contrast them with their comparatively low tech counterpart in Orion Shall Rise. Skyholm is a two kilometer wide aerostat hovering above clouds, mist and rain. Sunlight penetrating its double skin heats the air at its center that keeps it aloft. Solar collectors and thermal convertors generate electricity which:

runs the jets counteracting stratospheric winds;
supply on board needs;
beamed below, power synthetic fuel plants and other industries.

(Apart from Skyholm and a few local generators, the Domain lacks electricity because metal for conductors is too expensive. Anderson imagines a part past, part future period.)

Energy is stored for war or tempest. Skyholm lasers break a hurricane.

After the nuclear war, its international crew, the Thirty, moved this one surviving aerostat from its position above a now obliterated Paris to its present position above Tours and protected that city from desperate outsiders. The locals restarted the industries needed to maintain Skyholm whose skin, weakened by stratospheric ozone and ultraviolet, must be replaced piece by piece once a decade. Other areas accepted the protection of the Aerogens, now Thirty Clans: aerial surveillance provides safe borders, free trade, public safety, detection of crop diseases and rich fishing grounds, updated maps, weather forecasting and weather modification.

So, while the Maurai restored civilization in the Southern Hemisphere, this is what occurred in Uropa.