Tres de Febrero Park, also known as Bosques de Palermo, is a sprawling urban park inspired by New York's Central Park. Covering about 400 hectares, the park houses a rose garden, a lagoon with resident geese that beg for snacks, and a running path. Neighboring the park is a gastro-hub in the arches of the train tracks, a planetarium, and the Japanese Gardens.
You can rent bikes and roller skates to use on the path by the hour or even a paddle boat to paddle out onto the lagoon.
If you're hungry there are carts selling choripan, lomito, and bondiola sandwiches. Enjoy your street meat while others exercise around you (the best way to pig out).