If you want to give your credit card some exercise, head out to Santafé Mall in El Poblado. It's also full of great shops and restaurants, so you can spend the afternoon having a wander. Splash some more cash at Oviedo Shopping Center, Golden Mile, and La Strada Mall.
You can spend an afternoon browsing the exhibits at El Castillo Museum during your travels in MedellĂn. Check out the shops and top-notch restaurants in this walkable area.