I was going to post a couple under scenic runs but while I have seen some folks running these trails they are really great hikes.

And hiking is one of the best ways I've found to stay fit on the road particularly, as is the case with my first recommendation, when the hike is so close to downtown areas.

Camelback in Phoenix.

Old Rag in the Shenedoah National Park. Not near the city, but worth the trip!