Pyramid Hot Spring may be hard to find, hard to reach, and perhaps not even hot, but if you're prepared and daring enough to search it out, you may end up having an intimate hot pool located right on the cold water of the Kern River all to yourself!
First, the caveats: the natural boulder-lined pool is located right next to the Kern River, though the actual river level is higher than the pool for the majority of the year, and sometimes the entire year following an especially wet season. You must also cross the river to reach the springs. In the past this has meant hiking upriver and jumping across boulders and then a treacherous walk along a steep path to reach the spring. However, in 2016 it was only accessible by swimming across the Kern River. There have been numerous drownings on the Kern River in the past due to its swift current, so be aware of river conditions, your swimming ability, and definitely bring life jackets for all of those attempting to cross the river.
If you're able to actually find and reach the spring, you'll find a pool large enough for four people with water falling from a small hot waterfall at about 103 degrees. Though the pool is immediately across the river from a highway, a large boulder that sits in the river beside the spring shelters the pool from noise or any outside activity, making it feel as if you're in the distant mountains.
To reach the springs, park at the unmarked turnout (distances are key here, along with a single identifying marker of a large diamond-shaped boulder at the turnout's eastern end), and look across the river. Slightly downriver there is a large boulder jutting out of the river with two lower boulders exposed above the water's surface. If these smaller boulders aren't exposed, the river level will be too high for the hot pool to remain warm. Walk down the short slope on the downriver side of the parking turnout, and at the bottom, look for a spot to cross the river.
The hot spring may only be accessible during the driest late-Summer months. On a visit in late-August, the river level was still almost flush with the hot springs, and rags stuffed into the crevice between boulders were the only thing preventing cold water from mixing with the hot spring water. If conditions aren't good on your visit, a good alternative may be Remington Hot Spring a little further east in the Kern River Valley.
After a hot soak, swimming back across the Kern River will feel much colder than on the swim over, but it will rinse the slight sulfur smell from you.