[quote]We can make a mixture of technology levels, and a mixture of architecture this way too, the natives taking reference to build from what was left behind and what was shown in books and other such things humans left. We can have pockets of much more or much less developed styles here an there due to the humans visit.[/quote]

Following up on that, if anyone wants to pool resources from this idea:

One of my fictional worlds is based on the idea of an Aztec culture that was allowed to continue and blossom into an advanced society. It isn't set on earth, but instead it's backstory is that after Quetzalcoatl left earth he created a new world with a similar image. The people in this world have a mean level of 80s technology by the time the story set there starts, but their mythology and ancient monuments closely resemble Mesoamerican culture. That also has some impact on how their world and current culture has evolved, with new religions/belief systems splintering off from the original.