When you cross the bridge on the Donut Falls Trail, head over to the road. The trail is unmarked and heads off to the west. It can be a bit difficult to see. About 3/4 of the way up the trail you'll run into an old mine with the remnants of a cabin.
Then again near the top is a second mine shaft just off the trail. The second mine shaft is really interesting. After a short down climb you can follow the mine shaft through the mountain and emerge on the other side. From the top of the trail you get amazing views of a number of the peaks around you. This trail is steep and the climb is unrelenting.