The gondola system that runs from the metro up the steep valley walls to the once-isolated hillside barrios. Pay the normal metro fare (a few thousand pesos), ride Line K from Acevedo to Santo Domingo, and watch the city unfurl beneath you. The extension from Santo Domingo to Parque Arvi carries you across ridge and cloud forest; that leg costs extra but is the one to take if you only ride once.
Metrocable
Gondola lines connecting Medellín's metro to hillside barrios