Hello Folks,
Raven has got a good grasp of the setting I think. I usually use the anology of the Late Roman period mixed with the early Middle Ages (1000s). It's actually not unusual from what I've read and studied that tribal cultures lived next door to highly advanced cultures. The Germans, Celts or Goths all lived right next door to the Hellenistic Greeks and Romans at one point or the other and all interacted to a great extent. Even more "primitive" cultures such as the the Lapps and Finns (who did aquire ironworking skills) also existed well into modern times in Artic Europe. Really not that far fetched.
As for the ruling class living in palaces while the ruled lived in grass huts, well you've just described the Maya, ancient Kush, Zimbabwe, ect. It seems to a realtively common set up in the tropics. It seems that such "huts" are simply a matter of resources available. The houses of the peasants in Europe are of wattle and daub with thatch roofs. Comparatively similar in structure really.
Roman cities routinely had city-wide sewers (seen as cost effective as it kept down sickness. They saw cause and effect if not why), centrally heated bath houses open to the public (same reason as before), aquaduct fed fountains scatterd throughout the city (as before), and public flow-toilets (over twenty at a location). The rich and well off could have running water, central heating, and private flow-toilets. I would check out a few book on Roman enginering to get an idea of what a Iron Age civilization could do.
As for the towers and domes I would check out just what the Romans and later Byzantines and Arabs (who learned from the Persians and Byzantines) could do. Get some good books on such. I recommend David Maculay's books. Sure they are for children but the line illustration style makes for quick understanding, they are extremely accurate, easily understood, excellent for quick reference, and for showing examples to players. The books I use are "Castle" for a High Medieval castle (Harlech in this case), "City" for a Roman city, and "Cathedral" for a Gothic cathedral.
Some quick examples though of what I mean.
Until the Rennaissance the largest domes were built in Rome and Constantinople (both cities of over a million at their height) These rival any domes built in modern times still.
The Gothic cathedrals of the 14th cent. on were some of the tallest structures in Europe and the world outside the pyramids until the Eifel Tower. Some reached over nine stories tall or better.
The Coloseum held up to 75,000 (standing) and over 50,000 (sitting) and is still the blueprint for stadiums and the efficient funneling of crowds to this day. It still has not been improved upon. The Circus Maximus held over a quarter of a million for chariot races and rivals many Olympic forums to this day in size and granduer.
The Greek designed theater enables a person sitting in the last row to hear a whisper from the stage and once again has never been improved upon engineering-wise. Never underestimate our ancesters.
The Romans also had something resembling a modern open air shopping mall and a psuedo-stock exchange.
I'll say one thing, while slave labor makes much of what the Romans built possible (I'll leave it to GMs whether you use the Roman-style mix of skilled and unskilled slave labor) and more than a couple of Kingdoms have the wealth needed, many lack the Roman level of organization or their drive. I see only Auqilonia and maybe Turan having this scale of organizational skill combined with the drive. Sure it would be only to keep down unrest and disease, but I see the Church Of Mitra approving.[/u]