Parque Nacional Bosque de Tlalpan is a large wooded reserve in southern Mexico City, with walking paths, picnic areas, and a 5 km jogging circuit. It is one of the easiest places in the city to get under trees without leaving the urban area.
Come in the morning for cooler air and more local life on the paths. The park is practical rather than manicured: good for a walk, a run, or a quiet break after visiting Coyoacan, San Angel, or the UNAM area.