Nairobi is a tough town, and there’s no place in Nairobi that’s tougher than Kibera, Africa’s largest slum. Maybe a half-million people live there, maybe a million. No one’s really counting. But virtually everyone is desperately poor, with per capita earnings averaging about a dollar a day. Rape, assault, and murder are simple facts of daily life. The streets are paved with rotting garbage, sewage flows in the gutters, disease is rampant, and city services are largely nonexistent.