Designers are intervening in some of the world's poorest and most chaotic urban areas, helping residents come up with ingenious solutions to problems of shelter, access, services and schooling. Apainting project has brought art to the Santa Marta favela in Rio de Janeiro. Below, images from before and after a walkway upgrade in La Vega, Caracas, Venezuela. Haas&Hahn; Below, Photographs by Proyectos Arqui 5 C.A.