Moon Bases are structures similar to Terraformers, but constructed on a moon. Each Moon Base level completed creates three additional lunar fields, allowing for the building of other structures, such as Jump Gates and Sensor Phalanxes. Moon Bases must be constructed first to provide space for other lunar buildings, because new moons only have one available field. Building a Moon Base always requires an open field; if your moon is full and you want to add fields by building another base level, you will first need to destroy one other building to make a field available for a new Moon Base, which will in turn provide three new empty fields.
Once built, a Moon Base can never be deconstructed. (see also Moons in “Chapter 4.6, Combat”)