Carlos Paz is a great place for outdoor lovers, with activities like swimming, snorkeling, water skiing, jet ski, windsurfing, sailing, canoeing, canyoning (a form of rappelling), rafting, golf, tennis, parascending (flying with a parachute-like canopy that is usually pulled by a land vehicle to launch), hot-air ballooning, boat trips, horse and donkey riding, go-karting, an RC aeromodelling field, basketball and fishing.
Serious climbers and adventure seekers should head straight for Tanti (but if you don't fall into these categories it's still a lovely place to go for a walk).
Though outdoor sports make up the bulk of things to do in this city, if you´re looking for alternatives there is an assortment of amusement parks waiting for you, along with a few museums and other activities.  Take a scenic ride on the aerosilla, hang out on the beach, or, if you're interested in astronomy, you might want to check out the Observatorio Astronómico located a little ways from town.