In Mount Hood National Forest, a day-trip southeast of Portland, you can find Bagby Hot Springs. Quite frequented by locals and travelers, it may not be the solitary pool in the wilderness that purists seek, but it is still well worth the visit. When you arrive there is a thirty-minute walk to get to the springs from the parking lot. The path follows a jewel-toned river as it winds through a mossy forest and ascends only at the very end to reach the springs.
There are two sources where the spring water bubbles up from the ground and flows though ingenious channels into the tubs at about 135 degrees F. Three huts house a number of private and communal tubs. The private tubs are huge tree trunks that have been hollowed out and are long enough to fit two comfortably. The communal soakers are big barrels. The tubs empty and refill with channels and plugs so if you get a private soaker you can be sure to have clean water, and there are buckets available to collect cold water and adjust the temperature to your liking.
There is a society, Friends of Bagby, who maintain and protect the springs, and who gratefully accept donations. However, Bagby Hot Springs are often a victim of vandalism. I was initially put off by lurking trash and graffiti and was very glad I brought my flip-flops for walking around the site. However, in the end the water was luxurious and nothing else mattered. I even took the opportunity to cold plunge once or twice in the river to refresh myself and prolong my stay.