This thing is going to be conundrum for archaeologists if historical records don't survive.
- Is it a religious site like a pyramid, church, or stonehenge? Nope.
- It sets up all sorts of star alignments consistent with constellations as they would have appeared when the site was built. Was it a facility for astronomers then? Nope.
- The local people must have overwhelmingly supported such a project for it to have been built, right? Nope.
- There must be others like it indicating some form of regionally distributed cultural practice? Nope.
- So much effort went into building it that it must have been intensively used, right? Nope.
The only reason I think they might get the right answer after all is that there is going to be so much weird stuff preserved, even as a tiny fraction of the weird stuff that exists today. Our civilization is such that a single individual with enough money and a dream really can just do something, a sculpture or monument in metal or stone, that will last for millenia. That's before we consider the profusion of dead but obviously high-tech and resource-intensive artifacts we'll leave behind in their millions, cellphones, cars, even VCRs... A lone individual has, by the standards of any other age, quite a lot of power. That will show in the record.
I'm reminded of the old quote: "We considered ourselves to be a powerful culture." We're not entirely wrong.