Mexico City forms the core of the Federal District and is the commercial, industrial, financial, political, and cultural center of the nation. Among its diverse and important manufactures are chemicals, petroleum, food products, textiles, automobiles, machinery, pharmaceuticals, and consumer items. Population has increased rapidly in a city that had already spread out into many residential sections called colonias. Iztapalapa and Gustavo A. Madero are the largest suburbs of the Federal District; Coyoacán is the oldest, with a palace built by Cortés. The metropolitan area of Mexico City is currently the largest in the world, but it suffers from severe overcrowding. There are many run-down neighborhoods without essential services and large areas inhabited by squatters; it is estimated that close to one third of the city's residents are without sewage facilities.