For this project, I envisioned a city constructed on the recently discovered exoplanet TRAPPIST-1d by the stranded crew of a failed mission. Unable to return to Earth and left with the knowledge of its destruction at the hands of a nuclear war and global warming, the crew begins a frantic effort to preserve knowledge of Earth as they knew it for future generations. Built within a system of springs, waterfalls, and caves, the small settlement created by the original crew (listed as 200 members in the image above, but later increased to 2,000 for plausibility reasons) grows over decades and centuries into a small civilization, with a culture founded on deep reverence and appreciation for the history of a home planet they've never known. This mock-textbook page contains an early map of the cave system drawn by the original captain of the crew, as well as a fragmented explanation of the history of the central city's foundation.
Preliminary thumbnail sketches of potential scenes around the city
The tidally locked planet orbits a red dwarf star, never rotating to create day and night cycles. This leaves the planet largely uninhabitable due to extreme temperature differences and powerful winds, except for a narrow strip around the circumference of the planet called the terminator. Along this line, in a land of perpetual twilight, the lost crew found a new home. Located in a rain shadow, the fledgeling society gets its water from a natural mountain spring fed by the perpetual rainstorm on the other side of the mountain it is built into.
This view of the city shows a tableau of the city's core with a distant view of the botanical district, located outside of the man-made cave. With scarce and dim natural light, the inhabitants of the city proper create their own sun, as it were, through artificial lights. These lights illuminate the subterranean city through the lantern-like windows of its carved rock buildings, which do not contain glass due to their protected location within the cave. Travel is done on a man-made network of rivers and canals fed by the waterfall at the cavern's mouth.
This view of the city shows the innermost city limits, which are marked by a large cavern through which a waterfall runs. The deeper cave system is largely unexplored due to the mysterious flora and fauna that live there. The cave is composed of a rock similar to limestone, which is water soluble and easily carved.
This sequence shows a rare day of rain in the city, which creates a flash flood.