Ancient alien ruins

As they trudged over a rise on the apparently barren alien planet, they came across the ruins of an ancient settlement. In the immediate foreground were some sort of mechanical structures - whether they served the purpose of ventilation or power generation or some other purpose they could not say - and there was some sort of dust-covered artefact in the hillside on their left. All of this was covered in drifts of sand and rock, and showed signs of corrosion and sandblasting. What was most striking though was the iridescent blue disk to their right, which seemed as if it had been manufactured and set into the rock face only yesterday. The object - whether an access hatch or a window or some sort of sensor they could not tell - glinted in the light of the nearby star, and they felt drawn to it as if to a magnet.