Medellin put a cable car into its public transport network in 2004, running gondolas up to the steep northeastern barrios that buses could not serve properly. It is still the thing the city is best known for in urban planning circles, and from a visitor's point of view it is the cheapest and most honest overview available: you ride at rooftop height over neighbourhoods most tourists never walk through, on a normal metro fare. Linea K from Acevedo is the original. Ride it in daylight, and keep the camera discreet.