The spatial complexities partially arise from the incredibly varied and hilly terrain. The city had to adapt and densify within a very small area, which is the reason today's roads, multi-level walkways, sky-bridges, covered and semi-covered pedestrian pathways, escalators and who-knows-what-else all cut through buildings and link the high-rises, shopping malls, and the ‘normal’ exterior streets together in a crazy 3D network. The surrounding hills on one side and the water on the other side just don’t permit an easy suburban sprawl which is so typical of North American cities.