This trail is located in the Phoenix Mountains Preserve in north Phoenix.
This trail can be taken in either direction, and there are several access points. The most convenient parking area is the Central Avenue Parking lot at North Central Ave and East Aster Dr., at the north end of the loop, but on warm days, that lot fills up by 6 a.m. Alternative parking is located at the North Mountain Visitor Center, 12950 North 7th St, and then accessing Trail #306 from Trail #100.
The counter-clockwise direction is described here.
From the parking lot, follow the rough dirt road, for 1.3 miles, to the junction with the spur road to the summit of Shaw Butte. The climb from the parking lot is steady, but reasonable. From here, you can look out in all directions. The summit has several fenced off areas for transmission towers, making access to the best views difficult.
Returning down the spur road to the trail, you can continue the loop, turning left at the junction. In 0.2 miles, another spur trail goes off to another small peak. The views there are better, actually, than from the higher summit.
The trail now drops steadily, sometime steeply, and in many places, you'll be running on singletrack, to the valley floor. Use caution and have patience for people coming the other way. At the bottom, the trail follows along with Trail 100 - Charles M. Christiansen Memorial Trail
, for about 0.2 miles, then diverges again as it continues north to the parking lot.
On this trail, you'll see lots of hikers, runners, mountain bikers, and occasional horseback riders.