The Great Wall of Mars was a terraforming project on Mars created by Sandra Voi before the outbreak of the Coalition-Conjoiner War. A circular ring composed of a wall hundreds of meters thick at its base and tapering off to microns wide towards its two hundred kilometer height, it was designed as a shortcut to the otherwise centuries-long terraforming methods. The massive wall trapped a livable atmosphere, with the walls themselves slowly expanding outward at a rate of twenty kilometers per year, widening the living space.

Unfortunately, the wall was damaged during the Coalition-Conjoiner War, after which time the wall's self-repair systems were directed manually by Felka, a young Conjoiner with savant-like abilities.

It was eventually destroyed fifteen years later during the Coalition's assault of the Conjoiner remnant.