Terwilliger Hot Springs in Rainbow, Oregon

Two miles east of Rainbow, Oregon, along the McKenzie River Scenic Byway, a southward turn onto a paved forest road leading to the Cougar Reservoir eventually gives way to a decently-maintained, although somewhat stomach-churning, gravel track. Follow the cliff-hugging road overlooking the reservoir for seven winding miles to a small parking lot in the Willamette National Forest, bearing the name Terwilliger Hot Springs.

From there, a short half-mile hike grants visitors access to four tiered pools of natural, sulfurous, piping-hot volcanically heated mineral water, cascading down from top to bottom. The water cools slightly as it descends into each subsequent pool. Those who prefer their bathing experiences less than scalding are recommended to start at the bottom pool, resting at approximately 85°F, and work their way upward to the higher pools, whose temperatures range between 108° and 115°F.