The South Fork Walla Walla Trail is a great singletrack that provides a wide variety of running experiences. You'll encounter everything from smooth trail to rocky sections and short bits of exposure from the trees. There's also plenty of up and downs as well. The trail can make for a great multi-day trip or one long day run.
There are many loop and shuttle opportunities with other trails in the area like the North Fork Walla Walla
and Table Springs/Bear Creek.