'Terraforming Superstructures', environment concept art

"The terraforming on Sephin-DUA5 was rapidly undertaken to an industrial scale across all viable continents. It is deemed that negligence, and a lack of proper sub-surface reinforcement resulted in deep fissures forming across the planet's surface during the terraforming process. Once the fractures penetrated down as far as the mantle, a seismic gravitational collapse of the planet was triggered, and thus the project was deemed untenable. All engineers, scientists and colonists were evacuated from the surface shortly before a large portion of the planet collapsed in on itself. Sephin-DUA5 is now classified as inhospitable and is strictly off-limits."

Thumbnail exploration of some high-level environment concepts, from 2014.