Leave Medellín and head to the town of Guatapé in order to visit the enormous rock. The drive takes around two hours, during which you can appreciate the outstanding landscape of Antioquia. Guatapé has a reservoir created by the Colombian government for a hydro-electric dam. In the middle of the reservoir is the Peñol Rock. The Peñol Rock is possibly a meteorite due to its size. 

Walk up the stairs if you are full of energy (there are 654 steps to get to the top), to view the entire Guatapé reservation, this is an optional activity. Then visit the picturesque village of Guatapé where all of the houses are painted in quaint pastel colors.  After lunch (included), tour the Guatapé reservoir by boat (30 minutes) before returning to Medellin.