Environment: Penthouses for the Poor

Although about 2,000,000 of Mexico City's 9,000,000 inhabitants live in squalor, one out of every four of them has risen above the crime, noise and filth of street shanties. They occupy, with the city's tacit approval, hovels that they build on the flat roofs of solid buildings. While these penthouse poor prefer the roofs of small, low structures (where limited space holds fewer families and gives greater privacy), they gladly share the tops of taller buildings with each other, humming elevator equipment, water tanks and thickets of TV antennae.

This sensible use of empty real estate began back in colonial times, when employers billeted their domestic servants within easy beck or call in rooftop rooms. Nowadays the servants are joined by laundresses, window washers and security guards who exchange work for living space; other Mexicans pay up to $12 a month for a niche on a roof. The amenities, while sparse, usually include running water, electricity and enough room for a dog, a cat or a few chickens.

To be sure, the "islands in the sky" have drawbacks. For one, children must be constantly watched lest they play too close to the building's edge. For another, rooftop residents so prize their quarters that even when sick or poverty-stricken they hesitate to seek health or welfare services from the government. They fear that they would get landlords in trouble by calling attention to their unauthorized occupancy, or that conventional tenants would object if they heard of disease in the hovels above them.

Only the dwellers in other high buildings seem dismayed by the arrangement. Paying steep prices for their own apartments, they often discover that they look into a high-rise slum rather than over the grandeur of Mexico City.