The Big Dalton Creek, in Glendora, Ca, is little known outside the local trail community, keeping it relatively quiet, even on holiday weekends. It consists of several short trails and a few longer ones of varying difficulty, making this trail park one of the best for workouts and consistent training. You can easily vary the length of your run from 1 to over 12+ miles with elevation and steepness variation to match!
The video above is taken from Big Dalton Trail, which runs alongside Big Dalton Creek. It is a gently undulating 3 mile out and back hike that I like to run as a warm-up to a long run, or to add mileage or cool down after a tough workout on the steeper climbs.