I'm standing on my hotel balcony, looking out over the cars on Pretoria Avenue. Across the five-meter-high barbed wire fence, past the road, three perhaps homeless men lie on the grass. Some women try and make a few Rand selling newspapers on the street corner near the traffic lights (or "robots"). Beyond the lights, a Mercedes Benz dealer glimmers of new chrome and shiny credit cards. Welcome to Sandton, Johannesburg, South Africa. For the next two weeks, this place is home to the World Summit on Sustainable Development.

It's a decidedly strange place - and the paranoia about (and reality of?) crime is only part of the mix. Strange in that it mixes all the luxuaries our world has to offer with grinding poverty. Five star hotels, a huge convention center, multi-storey houses on individual leafy blocks, and a whopping shopping mall containing everything from The Body Shop to designer clothing boutiques. But go to any number of neighbouring Joburg suburbs and you'll find where the majority black population live without proper access to drinking water, the air polluted, the people often unemployed.

Yet in another sense, it's not so strange at all. As a city, Joburg mirrors the wider nature of our planet Earth. As in Joburg, a majority live poor, if not in poverty, while a minority live rich, consuming most of the resources; the two separated from each other by immigration procedures and fortress-like borders. The difference here in Johannesburg, and what makes it unusual as far as global cities go, is that these two realities physically intersect.

While it may be uncomfortable for diplomats used to the refined boulevards of Geneva (those trekking from New York might be a little bit more at home), hopefully, the location will help galvanize them to the ambitious but vital task at hand. That is to find a way to bring about an end to poverty and create prosperity without sacrificing nature or wasting the scarce resources of our planet in the process. The stark contrast in Johannesburg is therefore a strong reminder of the inequalities that face our world, and it makes the city a fitting place to host the World Summit.