If you’d like to try a hot springs in a natural setting, head for Terwilliger Hot Springs, located in a forested canyon at the end of a 0.25-mile trail. Hot water bubbles up out of the earth at 116°F and flows down through a series of log and stone pools, each one a few degrees cooler than the previous one. A series of access steps and railings have also been built to help you get to the various soaking ponds. The local custom is to forgo the option of clothing.
The several pools in this tranquil forest setting can be overcrowded on weekends. Although this hot spring offers an exceptionally nice soaking experience, it can occasionally attract an unsavory crowd. As with all of the more remote and wild hot springs, take a friend.
To get there, take the Aufderheide Drive [1] from Route 126 south toward Cougar Reservoir. The trailhead for the hot springs on the west (right) side of the road is marked by a sign just past mile marker 7. You can park in a large lot on the east side of the road about 500 feet past the trailhead (alongside the reservoir). Parking alongside the road is prohibited (and enforced) from sunset to sunrise 1 mile from the trailhead. A $5-per-person day-use fee is required, and it has enabled this place to be well maintained.
Links:
[1] http://www.moon.com/destinations/oregon/the-willamette-valley/the-mckenzie-river-highway/sights/aufderheide-national-scenic-byway