Near Greenwater, the 16 mile Sun Top trail (#1183) is a challenging loop with 3200' vertical and vistas of Mt. Rainier. To reach the mountain biking trailhead from Seattle, head south on US5. Follow SR410 east for 6.5 miles through Greenwater and turn right on FS73. Park just across the bridge.
Continue riding up FS73 and turn left on FS7315 to the lookout tower. Climb for 6 miles up 2,800’. Just before the summit, the trail begins on the left (before the parking area). On the trail, continue climbing over the next mile before starting a wild descent. Stay left at all forks and downhill across all roads.
At the intersection with FS71 near the airport, head past the airport. Before the wooden bridge, turn left on the Skookum Flats Trail for a 6 mile technical singletrack back to the car park.
Overall, Sun Top Loop Trail is the 39th most popular mountain bike trail of all 59 mountain biking rides in Washington.