When in the Eternal City (aka. Medellin, Colombia), there are ALOT of things your recommended to do as a tourist. You'll hear alot of suggestions to take the Metrocable, as well as check out Parque Lleras in Poblado, Medellin.
From my personal experience I have done both those things, and although they were fantastic, if your only in Medellin for a day or two I recommend adding Plaza Botero to the list.
I personally really enjoyed visiting Plaza Botero and the Museum of Antioquia (which holds many works of art by Medellin's most famous artist Fernando Botero, known for both sculptures and paintings). Throughout the plaza are many sculptures that were placed so that the public could enjoy art without having to pay entry to the Museum of Antioquia.