What do the Archbuilder ruins represent in the novel, Girl in Landscape?

The Archbuilder ruins symbolize the Archbuilders’ previous struggles and activities. The Archbuilders ceased building edifices after the made the climate temperate and had no need for shelter. Also, most of the Archbuilders left the planet in order to explore other parts of outer space. Nugent views the remaining Archbuilders to be idle and useless, like the ruins.