This is a huge artesian limestone pool that has been used my man for at least fifteen centuries.
Around the warm water (75F) are various old habitats including these old cliff dwellings.
The water has a natural drain which goes into this creek on the other side of a cliff. The tree rising up from the creek bed is an Arizona Sycamore. Take a look at this view of it. (you can click on any picture to enlarge it)