Before the creation of ExterNovan, before the decline of Novan civilization, there was a revolution in architecture. Though much space was created after the Great Migration, it was quickly filled by the Novans. By 4200, population density had become the most pressing problem. Too many people were unwilling to settle in colonies on the outlying moons. It was then that the ‘grid’ system was born. Whereas before buildings towered at most 120 stories in height, the grid system allowed buildings to stretch up to 400 stories. This was accomplished by a segmented support system, but more importantly, by running connecting passageways between buildings. To start, four buildings were constructed, each structure the corner of a square. Then, at the bottom and middle third of each building, connecting beams would link one building to another. This square of buildings would be used as a kernel, around which whole cities would be built. Though the grid system provided space for the first time in many centuries, it also began the eventual separation of classes that the construction of ExterNovan cemented.