I posted this as a comment inside another post, but here it is on its own:
Something else to think about – Old Pavis went through a couple of historical stages, we should be able to see in the city’s current architecture:
Golden Age. 831-924 (93 years). This is when the great structures of Old Pavis were built by the dwarves out of stone quarried from the Faceless Giant. This period lasted less than a century. Lord Pavis himself retired to his temple in 860, so he was only around for about 30 of these years. After that, the city was attacked by Thog the Giant and an army of trolls and nomads. The city was reclaimed in 877, and after that an era of prosperity and growth followed (877-824). Pavis likely had a population as high as 50,000 at its peak.
Foes of Waha. 924-1237 (313 years). This is a long period of decline. The Golden Age buildings were quarried, cannibalised, or turned into fortified strongholds (Opili’s Fort, Mani’s Fort, Real City, Zebra Fort, Angle Fort, Balastor’s Barracks, Old Flintnail Fort, and the unnamed Old Walls on the other Twin Hill). Thanks to the dwarves, the quality of this construction was still very high – and much of this construction was underground, linking the various strongholds together. The city’s population was no more than 10-15,000 people, and probably less. Nomads sometimes made their way within the walls, but were always forced out again. The Garden expanded greatly during this period.
Troll Occupation. 1237-1539 (302 years). The trolls rule the Big Rubble, occupying Opili Fort. Several other forts abandoned or destroyed (Old Walls, Angle Fort, Old Flintnail Fort, Balastar’s Barracks). Dwarves build New Flintnail Temple and maintain Real City – but otherwise most construction and maintenance is of low quality. Almost all construction is underground. Human population of the Big Rubble is maybe 1000 people and they are effective slaves of the trolls.
New Pavis. 1539-now (86 years). The Real City and Zebra Fort allied with the new Sartarite settlement. Trolls largely confined to the Troll Stronglands. Human population steadily grows despite emigration outside of the city. Indagos family of the Real City claims tracts of land in Pavis County, securing greater food supply and wealth.
Now something I find interesting is New Pavis has already been around nearly as long as the Golden Age of Old Pavis lasted.
So if we imagine Pavis at its height as having 50,000 inhabitants, it lost some 80% of its population during the Foes of Waha era, and 98% of that population in the Troll Occupation. Another way of looking at it is that during the Troll Occupation 98% of the former human city was devoid of human inhabitants, and free to be claimed by others. Mainly trolls.
Although the city was definitely run down during the Foes of Waha era, it was just empty during the Troll Occupation. Nobody to maintain or repair buildings, and buildings were looted for parts if they weren’t outright destroyed by the trolls. And that went on for centuries….
For a population that size there must have been a lot of farm land to support them. Where would that have been? The Zola Fel valley. Once the nomads took that over, Pavis quickly lost 80% of its population and never recovered.
Do the nomads still hold the valley? In 1625? No. Pavis County is settled by mostly Sartarite farmers, and Sun County is a stronghold of Yelmalion farmers. The Lunars made a failed attempt to settle the lowest reaches of the valley.
Given the population of old pavis was much larger than new pavis, is there a lot of deserted farmland? Yes. Lots of traces of irrigation systems as well.