Enjoy the soothing waters
Agua Caliente, was named for the hot water spring which was used as a spa from pre-European times until the water was drained dry by farmers & ranchers in the late 1940s. I read somewhere that the Indians who massacred the Oatman family stopped here for a relaxing bath with their two young captives, Mary Ann and Olive Oatman. On March 30, 1862, nearby Stanwix Ranch / Stanwix Station, a stop on the Butterfield Overland Stage, was the site of the western-most battle of the Civil War. The California Column, of that war, also stopped at the Agua Caliente hot springs to partake of the soothing waters. The reputation spread, and in 1897 a 22-room spa was built. The spa was used during World War II by the officers (of course) of nearby Camp Horn.
The spa building is still standing, and intact, but it is signed off with "no trespassing" warnings. There is also a large satellite antenna outside. It looks like the grounds are occupied, so best take any pictures from the road. Just southwest of the spa, on the west side of the road, is an intact old stone building, which is fenced off and has metallic screens over the windows. The rest of the Agua Caliente, on the east side of the road, opposite the farm, is free to explore.
The stone buildings of Agua Caliente are all in ruins, with only one small shack still standing. In all, there are the remains of several dozen buildings, some fairly substantial. The largest building, with most of the walls still intact, is about 25 x 50, and surrounded by a curtain wall, either to form a courtyard, or as fortification against Indians and/or bandits. Other than beer bottles, the only identifiable artifacts were a couple of small refrigerators. (The type with a small inner box that serves as a pseudo-freezer.)
On west side of the road, the Pioneer Cemetery has burials from 1880 to at least 2007. More recent burials at the south end, older at the north, nearer the ruins. I found at least one grave that was obviously empty. (Spooky.) Many of the older graves are marked with only a wooden cross, or have no remaining memorial and are now only mounds.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.