Sol always stuck out to me because, to me, these ruins don't seem alien, not really anyway. It's my hunch that they were made by The Missing, humans who left Sol long ago, and maybe found something interesting, advanced, dangerous, something big enough for them to justify leaving ruins behind as a message to us as we follow in their footsteps.
Just a hunch I have, especially seeing how the map lines up with SOL as the pyramid point so precisely.
Could all be an outlandish coincidence too, I admit...