If you’re looking for more than just a one day trip then Rio Claro is a great option. Just three hours east of Medellin Rio Claro offers the chance to get up close and personal with Colombian flora & fauna whilst also being able to participate in various outdoor activities such as rafting, caving and zip lining through the canopy.
http://www.medellincolombia.co/medellin-sightseeing/visit-nearby-towns/