[ he nods, and wonders to himself if heliobi would even deign to haunt this place. it all feels terribly hollow. ]

It does eerily remind one of a tilled field, does it not? The spacing of these cavities is not as orderly, but there is still a sense of regularity to them.

It's as if these machines were harvesting resources, or planting them. It could very well be both your suggestions.

Given the shape of these cavities, however... [ sure looks like people! ] It is difficult for the imagination not to take a grim turn.