For Hong Kong's elites, elevation - The Peak, anyone? - is clearly a virtue. Top-floor bars and restaurants are, of course, invariably high end (geddit?) while in certain circles - particularly expat circles - having oneself a rooftop to cavort on is worthy of considerable envy.

But the view from the top is not unblemished. Hong Kong's sprawling rooftop slums - networks of tin shacks and makeshift structures clustered atop old tenements in neighbourhoods such as Kwun Tung, Tai Kok Tsui and Sham Shui Po - may be hidden from sight on street level but lofty vantage points reveal their less-than-glorious reality.

For their tenants, living conditions are generally miserable - the accommodation is often shared with rats and the buildings' dark stairwells attract drug users. There is also the constant threat of eviction by landlords breaking whatever legally dubious contracts may exist.

With demand for public housing outstripping supply, however, it suits the government to turn a blind eye. And indeed, in a town where housing costs rank among the highest in the world, these dwellings are sometimes simply the best option available. Those who scrape a living in these districts also save themselves the cost of commuting from remoter areas.

Besides the vast divide between rich and poor in Hong Kong, the existence of rooftop slums highlights the desperation of many locals just to make a living. If nothing else, they are a standing reproach to the chattering classes' mania for roof space.