Sometimes things go wrong. You make an ocean on the Moon, it sublimates too fast, and you're left with a tanker rotting on regolith. But there's still a beauty in it. You've made an ecosystem, no matter how brief and pointless.
Still, if you go to the trouble of salvaging and repurposing some cast-off terraforming rig, you don't want to make a mess of things. You've got to pick someplace where the environment can be tweaked, but not scorched. The point is to make the kind of environment that Big Eco would never allow. Something extreme or impossible in a wild type ecosystem. Fuck those bland Cretaceous jungles and Pleistocene savannas; Earth nostalgia is the worst motive for reshaping a world.
For years, the four-person crew of the Callenbach created environmental installations on small moons and planetoids, leaving gas behind where there had been only vacuum and injecting barren ice fields with cyanobacteria that bloom into bizarre streaks of red, purple, and gold.
What most people don't realize is that the entire ecosystem of Nocturne, right down to the city-ready mangroves, grew out of a Callenbach project. If you ever visit the place, remember that everything you see was conceived deliberately to defy your expectations of what a planet should be like. Patches of open land burst bi-annually into orderly lines of edible plants. Trees grow warm rooms beneath their xylem, and biting insects carry vaccines. Every piece of life was designed with human civilization in mind, to prevent the most basic problem that comes with colonization: The destruction of so-called hostile ecosystems to make things comfortable.
It may have started as a work of art, but it became a new kind of life.