Cities need infrastructure like roads and networks to function efficiently, but they can't just be built anywhere. As cities grow, they develop a hierarchy of infrastructure, from local roads to highways and subway systems. However, as cities become denser, the infrastructure takes up more space and needs to be placed in the third dimension. This includes roads, electrical cables, fiber, and pipes for water and sanitation. These networks grow in volume faster than the underlying space, leading to crowded and disorganized cities if not properly planned.