Is it ever possible to build on Ruins?

I'm fairly new to Endless Legend, and one thing keeps throwing off all my plans. After I search a Ruin (of any sort) and the glow goes away, I forget it's there and try to build my city/districts and the Ruins keep getting in the way! After they stop serving a game purpose (that I'm aware of), is there a way to knock them down or otherwise build in those hexes?