In the fall, I will be teaching a course in urban anthropology at Rutgers University-Newark. This has been an opportunity for me to rethink my own experience with the cities where I lived. Trento, the city were I grew up. Palermo, the city where I became an adult. New York, the city that made me a world citizen. Medellín, the city where I did most of my fieldwork. In Palermo and Medellín, especially, I went in touch with dark side of our societies and democracies. It was an encounter with the murkiness of our realities and with the gray areas where the boundaries between legality and illegality blur. Here are some notes I took about Medellín. There are invisible boundaries running through Medellin, and invisible walls facing off one sector from the other, thus dividing up the city into poor and wealthy barrios. The well-to-do people withdraw and segregate themselves in the private enclaves of El Poblado or San Luca where they live in fortified villas or luxurious condominiums. As anthropologist Teresa Caldeira noted in her study of crime and segregation in the Brazilian capital São Paolo, "the upper classes have used fear of violence and crime to justify new techniques of exclusion and their withdrawal from traditional quarters of the cities."