Last summer, I lived in Lima, Peru, researching how tuberculosis disproportionately affects the city’s most vulnerable populations. Geographically, Lima is compressed between the Pacific Ocean and the foothills of the Andes, creating an acute scarcity of flat, buildable land. As a result, many of the city’s poorest residents are forced to build their homes on the steep slopes of los cerros, informal hillside settlements that constitute Lima’s most impoverished neighborhoods. This is a photo of Rimac, one of the most precarious settlements in the city, where it’s estimated that around 4,000 homes are at risk of collapse. 

While I have seen such settlements in other South American cities, I was struck by how this stark altitudinal stratification—a kind of vertical inequality—shapes daily life in Lima. An invisible line separates those who live at sea level, with access to services and infrastructure, from those whose homes ascend the mountains, mapping socioeconomic and even health disparities directly onto the landscape.