Assuming the photo shows walls that were once above ground, I don’t quite understand the process that buries structures like that, even over several thousand years. I can understand places like Mexico City where the Spanish built upon old Aztec structures but what causes soil to pile up like that? Or do people intentionally bury old places after they’re abandoned?
It’s two things. First, the only cities we CAN find are those that were buried. The others have long worn away, or their materials used for some other building. Survivorship bias.
The other thing is that cities and the people that inhabit them produce waste. Bringing stuff in to eat, wear, use, burn, etc is crucial. Hauling it back out when you’re done, less so. So stuff piles up. Pottery bowl breaks? Throw it in the back yard. Shirt is worn out, throw it in the back yard. And of course, there’s the human waste, too, obviously. Anyway, all that stuff piles up, and eventually the walls are half covered. You then either build anew on top of the rubble , or you move the town and it stays buried, or half buried.
Good call, babble-on! Also,it depends on the site. Erosion, windborne debris, earthworm activity, the crumbling of the ancient structures, reuse by building over the older habitations, and (my personal favorite) using the abandoned town site (or parts thereof) as a refuse pile all can contribute to the burial.