The Brazilian interior is a raised plateau — called the Brazilian Shield — which directly abuts Brazil's Atlantic coast along nearly the entirety of the country's southeastern perimeter. The drop from the shield to the Atlantic is quite steep, with most of the coast appearing as a wall when viewed from the ocean — the source of the dramatic backdrops of most Brazilian coastal cities. This wall is called the Grand Escarpment, and most Brazilian cities in this core region — Rio de Janeiro, Vitoria, Santos and Porto Alegre — are located on small, isolated pockets of relatively flat land where the escarpment falls to the sea. The primary problem this enclave topography presents is achieving economies of scale. In normal development patterns, cities form around some sort of core economic asset, typically a river's head of navigation (the maximum inland point that a sizable cargo vessel can reach) or a port or nexus of other transport options. The city then spreads out, typically growing along the transport corridors, reflecting that access to those transport corridors provides greater economic opportunities and lower economic costs. So long as somewhat flat land remains available, the city can continue growing at low cost. In time, nearby cities often start merging into each other, allowing them to share labor, capital, infrastructure and services. Economies of scale proliferate and such megacities begin generating massive amounts of capital and skilled labor from the synergies. The Grand Escarpment comes right down to the ocean throughout the Brazilian southern coast, however, and Brazil's cities therefore are forced to develop on small enclaves of relatively flat land in the few areas where the escarpment has not pushed all the way to the sea. The lack of a coastal plain means no small cities can form between the major cities.
