The small town of Guatape is a colourful and tranquil pueblito (small town) perfect to enjoy a day trip (or two) from Medellin. Whilst the town is famous for the colourful designs on the facades of the houses it’s probably more recognisable in promotional material for the the large rock “El Penol” which you can climb to get an amazing view of the surrounding man-made lagoons.
http://www.medellincolombia.co/medellin-sightseeing/visit-nearby-towns/