For the cost of a metro ride in Medellin you can transfer at Acevedo station to the Metrocable line, a gondola system that will whisk you up the side of a mountain to Santo Domingo. The ride is comfortable, and the views are stunning.
Traveling over some of Medellín's poorest neighborhoods, you will see communities in action. You might see kids splashing in a pool or riding scooters on a playground, or you might spot someone hanging their laundry out to dry, or you might spot a rooftop card game in full swing. On a windy day you'll be amazed at the number of kites flying above the red brick homes stacked up the side of the mountain.
At the top, you can either transfer to another line to travel to the Parque ARVI for outdoor activities, or visit the impressive Biblioteca España nearby.