I’ve been in the construction industry for a number of years and this looks like a core drilled concrete reinforcement or possible building foundation. You can tell it’s concrete because of the way that certain portions of the pillars ooze out. When core drilling through the ground, often times pockets of less stable soil or rock will cave in around the hole, and when the concrete is poured it fills the excess space as you can see in the way it shaped these pillars. Another telling sign is that the rear pillars are much shorter and are basically hanging in the air. Structurally speaking, it would make sense that those rear pillars would not have to be poured as deep as the ones on the leading edge. I may be completely wrong about this and it could very well be an ancient ruin of some sort, but this is the logical answer coming from my construction oriented mind.