Is it possible to visit Piedra del Peñol and Guatapé in one day?

Of course it is. It is possible to do everything in one day from Medellin, even on your own. In case you do it this way we advise you to take one of the first buses or busetas, they start at 5:30-6am and take the last one at 8pm to return to Medellín from Guatapé. In this case, the first thing would be to visit the Piedra del Peñol, telling the driver to drop you off there and after the visit, take a moto-chiva (tuk tuk) to go to Guatapé for 10000 Cop, do the visit and then return to Medellín. Another option, if you don’t want to worry about anything, is to book this Guatapé Excursion + Boat Trip or this Guatapé Excursion, both with a Spanish speaking guide.