The Peavy Arboretum, on the north edge of the city, is the research forest of Oregon State University, but it’s open to the public for recreation opportunities of all stripes. Here, runners will find about a mile of groomed gravel trails as well as access to the huge McDonald-Dunn Forest trail network.
This trail map has excellent information about the McDonald-Dunn Forest trails, including loop options and distances. The Powder House Trail/Section 36 Loop is a popular choice departing from the Arboretum, which leads to nice views of the Soap Creek Valley. It’s about 4.5 miles round trip. Some of the trails in the forest are wider/easier, and others are narrower and more rugged. It’s also a popular mountain biking spot, so keep a look out!