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In the 1970s NASA pursued serious plans to create space colonies at a “far-out address”—L4 and L5, two of the five “libration points” between two large celestial bodies (in this case the Earth and the Moon) in which a floating object will remain in a stable point relative to those two bodies.
NASA hired Princeton physicist Gerard O’Neill to develop the concept. O’Neill testified before Congress on the subject, and as a part of the work his team at the Ames Research Center, in collaboration with Stanford University, generated these wonderful images of human settlements in outer space. They come in three types—a cylindrical space colony; a “Bernal sphere” space colony, in which the people would live on the inside surface of a sphere; and a toroidal space colony (a toroid is essentially a donut shape).Go to Dangerous Minds for more images and to see a 70s era NASA video about O'Neill's concepts.