If you take the I-5 up to Bakersfield, hang a right on the 178, and shoot up north for a short stretch on the 14, you'll hit U.S. Route 395, a highway that starts at the Canadian border and culminates at the California town of Hesperia in the Mojave Desert. Head north, through Owens Valley, and you'll start to ascend the Sierra Nevada mountain range. That's when you start getting into natural hot springs country.
The area is littered with them. Here is a surely-incomplete list of five that are worth visiting.
Buckeye Hot Springs
This natural grotto of bubbling hot springs (including one tub that's been carved out of the mountain) sits near a cool river. The springs are a bit off the beaten track -- you'll need to go on a dirt road with your car, and perform a short, yet steep, hike -- but that's what keeps it relatively private.
Travertine Hot Springs
Nearby are the increasingly popular Travertine Hot Springs, which are three pools that feature interesting looking rock formations and incredible views.
Hilltop Hot Springs
In the town of Mammoth Lakes, near the Little Alkali Lake, sits this small, man-made pool that is fed by natural hot springs.
Little Hot Creek
Also in the town of Mammoth Lakes is this decent-size, man-made concrete pool that's fed by natural hot springs. The site also contains benches nearby to lounge when you're cooling back down.
Thirty-five miles north of the town of Bishop sits this concrete pool, the natural hot spring water piped in about 50 feet downhill from the source. Camping nearby is also available in pull-outs from the entry road.