The Hoyt Arboretum is 200 acres of local, national, and international trees. The park has a network of trails that are thematically named by the species you'll find along the way. From the holly to the white pine, the redwood to the oak, the trails are well marked and maintained over varied terrain. When you stand at the apex of the park looking down toward the zoo, you'll notice the remnant geography of a par-three golf course, a park feature decades ago.
There is an interpretive center with a gift shop near the top of the hill, too. The trails take you to the Japanese and International Rose gardens to the east. The Oregon Zoo, Forestry Center, and Children's Museum is to the south with the Vietnam War Memorial to the west.
The Hoyt is a central point for exploring all of Washington and Forest parks. It's part of a greenbelt that is the longest urban park in the country. With 1,400 species to explore, plan to pack a lunch. I run in the park and have no trouble getting in eight miles, but that pales compared to folks I meet out on the trail who are doing 30 miles in the woods. The Wildwood Trail is the centerpiece of the system and traverses the West Hills parks. Take the Max from downtown west to the zoo stop and see if you can find the monkey puzzle trees. You'll have no problem wandering off and getting lost in the middle of town.