As we’ve noted many times, the defining aspect of life in space is life indoors. But, what sort of life? Though the very grand, vast, fantastical spaces Marshal Savage described in the original TMP are likely to be a much later development, the environment of Avalon habitats, even in early periods, is likely to be far from claustrophobic and far removed from the military submarine environment of the pre-fab outposts commonly proposed. The most challenging aspect of the design of Avalon habitats will be the crafting of spaces creating an impression of an outdoor environment even though the entire habitat is enclosed and, for the most part, subterranean. Though most of us in industrialized countries today spend most of our time indoors, the sense of a relationship between indoor and outdoor