I went here at night (a great experience), then returned the next day to take photos.
After dark, the 25 mile drive from the park lodge to the hot spring in the desert lowlands along the river seems to take hours. The last two miles of rough dirt road descend a gulch where moonlight glows on steep cliffs of sedimentary sandstone. Each horizontal stone layer, only a few inches thick, is broken unevenly and stacked on the next creating an amazing variegated texture on the 50 foot cliffs.
At the bottom of the gulch you can hear the rush of the river and a warm desert wind buffeting the willows and reeds. On the bluff above the sandy parking area is an abandoned stone building. It feels restless and wild down here and, as you follow the dark path toward the sound of the river, wind rattles through the fronds of date palms next to more empty stone buildings with the pale jagged sandstone bluffs rising behind. This is what's left of an old hot springs town developed in the early 1900s.
The actual spring flows into a stone and concrete pool, which is all that remains of the old bath house down where the trail skirts the base of the cliffs by the river. Prehistoric petroglyphs on the cliff are evidence that people have come here for thousands of years. The pool is barely above the river level and juts out into a small set of rapids with Mexico only about forty feet away on the other side. It's a great place for a moonlight soak - in the day time it gets heavier visitation