Kibera is a shanty town of rusting roofs slung across mud, rocks and a rubbish dump.
Its half a million inhabitants live in single room mud huts and tin shacks crammed closely together.
The narrow paths between are often open sewers. There is no proper sanitation and little electricity.
The main railway to Uganda runs through it. Children play by the track and scatter when the train lumbers through twice a day.
Nairobi is just three miles down the line. But not much of the wealth of Kenya’s capital - home to more dollar milklionaires than most African cities - makes it this far.
Reputedly the world's biggest slum is a vivid illustration of the problems of poverty and inequality highlighted at the launch of today’s international campaign.
It is also a demonstration of the limits of the aid operation so far. Despite all the money and all the effort, many people here tell me life hasn’t got much better.
Salim Mohammad has worked in the slums for 15 years.
He’s the co-founder of a local charity called Carolina for Kibera.
Among its projects is one of few clinics serving tens of thousands of potential patients and a day care centre where we meet Mustafa, a malnourished nine month old baby whose mother, like so many here, is HIV positive.
Save the Children, one of the organisations behind today’s campaign, says none of this should obscure the giant strides being made around the developing world.
Over the past decade or so, there have been significant falls in the number of children dying needlessly from disease and a dramatic reduction in the numbers living in absolute poverty.
The new targets they’ve set are ambitious but they warn the world’s governments that if they duck big decisions at UN summits this year, the progress could be thrown into reverse.
There’s a fear that compassion fatigue might take a toll on a world struggling with austerity and beset by many other pressing problems.
Nowhere is that fear more keenly felt than Kibera.