Remnants of subteranian pathways of water drainage may still exist, even if they've become plugged up with sediment or collapsed over time. Some that remain may have been functional, whereas the larger rooms may only be revealed by their last remaining alcoves in high-wall location.
Note the arched rock above this alcove. This may be the remnant of a much larger void. The break in symmetry offers a hint of something obscure to be considered for it formation.
The bible tells us that the Earth's initial description was "without form and void" which could mean; lacking abrupt mountains and being highly cavernous.. This condition would be expected or understood if we were to consider that the earth formed in a weightless enviornment at extreme temperatures and possibly even tossed from its formation enviornment into the cold of surrounding space where its exterior cooled rapidly while the interior contracted further as it cooled, leaving highly porus regions under a fragile shell. But this early condition was very unstable and temporary and probably set up the conditions which led to some of the present features, but more recent events established structure for new features out of the violance involving the old.
A close examination of certain walls in canyons may provide important clues. In addition, an investigation of any reports of cave structures may provide clues to the determined efforts of the ancients to enjoy the enclosures where drainage pathways existed. Examination of the level of any potential infilling of canyons by water is important since natural dams could have created an inland aquatic environments not unlike the lakes formed behind modern dams, providing greatly simplified access to various habitats in places which are now inaccessible. The many flat areas within the Grand Canyon could have been quite usefull near an abundanance of water in storage there.
It is my expectation that these people were accomplished water managers before and after the world around them was changed physically and environmentally. These people were highly sophisticated and accomplished in ways that reveal that they were not detached from the rest of the world like this contenent appears today. They were also not detached from an inspiration source which could've been experienced more overtly in a more electrically charge enviornment.
Of additional importance was shelter against conditions on the surface -not like what we experience today,, except in its hints-of-intensity seen as the gentle emissions of the aurora. This will be more thoroughly understood as plasma-cosmology and comparative mythology determine the cause of high energy plasma formations in the local celestial realm which find comparable artistic representations in some petroglyphs. These high energy conditions are said to have been so intense that shelter underground or behind non-combustable structures was necessary. Many people did not survive the onslaught -and then cyclical- catastrophic events which are carried forward to us in myth and legends. Much is yet to be learned if we can only piece together the evidence through a cooporative effort that examines the outcome of an incomprehensible series of traggic event in a past which our great great ancestors barely survived.