Guadalajara seems like such a plain, flat town, but it is suddenly interrupted by a very abrupt plunge into La Barranca de Huentitan, a deep gorge that sort of discourages expansion to the west. There are several good vantage points to see the canyon, which is fairly spectacular--green and wooded with horses and cattle grazing way the hell down below. In the wetter seasons, the river drapes the north end of the barranca with a pretty waterfall known as the Cola de Caballito (Ponytail).
You can see the canyon well from the zoo--the Zoologico Guadalajara, way the hell and gone out Calzada Independencia ($1.50 US admission). There are buses.
Or continue past the zoo to the end of the line and enter a park with an open air restaurant looking directly down into the maw of the canyon. This is a great place to eat, sort of like a big barbecue that goes on all the time and serves anybody. Women cook over open fires and you sit on benches to look over the low wall that separates you from free fall.
Another great approach to the canyon is where the Amigos de la Barranca hang out, especially for the exercise-addicted. The Amigos' clubhouse is at the top of a unthinkably long set of stairs and paved paths leading to the bottom of the canyon (from which there is nowhere to go but back up that insane Stairway to Cardiac Arrest). And, you guessed it, they run down and back up. If you think you're hot shit for running marathons, try this vertical one and see how you do. If you make it back up, step over for a beer and some 'barbacoa.'