Maybe it lasts 5000 years or more and when that day comes, their archaeologists analyze all the alignments, the structure, the context, etc and conclude that it must have been an important part of a society that valued science and technology. They study it and postulate that it was a gathering place for people to visit on important days and they look for dropped or discarded items trapped in small crevices in the rocks from which it is constructed so that they can date it and categorize the lifestyles of those who visited or worked on it.

I wonder if there are modern parallels, like with Chaco Canyon. Was that site the culmination of one man's lifetime dream to put the things that he noticed about his universe in perspective so that his neighbors and anyone else who passed through the area could hang out and drink the local drinks, hooting wildly as the moon appears in a stone portal on a certain day just as he had told them it would. "BYO refreshments", he told them. There isn't much out here but it will be worth it if you come.

Maybe all the medicine wheels we find across NAmerica where the work of one old, learned Johnny Appleseed Native American guy who liked to watch the skies and saw how things worked in cycles. Over time he shifted a few rocks around so that to an observer, they would align on important days of the seasons. Perhaps he calibrated his wheels by chipping spirals into stones to mark the edges of shadows so that he would know when a cycle ended and new one was beginning.

One day he started a long walk-about, traveling across the country and staying in one place for a few years, just long enough to move a few rocks around to fit the local alignments that he recognized and then moving on to a new spot to meet the start of the next cycle. Or, maybe he passed that knowledge on to his kids who continued the work once he had passed.

I'd like to be around in 5000 years to read the guidebook they create for a site like this, where so far anyway, it has near zero utility and exists as a local curiosity with limited accessibility.