As an avid hiker, I've been lucky to find a great number of natural geographic spaces to play flute, these include colorful Echo amphitheater N.W. of Abiquiu, N.M. (where Georgia O'Keefe did a lot of her paintings). Natural Bridges is good as well as Arches N.P. which has plenty of intimate spaces (which provide more of a natural reverb effect than delay) some of these are difficult to squeeze into. Zion N.P. has some really cool places, two of my favorites there were way up a side wall in Hidden Canyon & Echo Canyon passage (AKA the Catwalk) Which both have a nice combination of echo & delay. The trailway unfortunately got wiped out by a rockslide in 2019. Utah of course has lots of slot canyons that all sound nice, one in particular is Buckskin gulch which also has cool petroglyphs, this canyon is very colorful. My all time favorite place to play (so far) is an absolutely beautiful canyon called Singing Canyon UT. it's a long way from nowhere but the acoustics will make your hair stand up! A great combination of reverb and what sounds like a multi-tap delay! If I could only carry a bunch of recording gear there. Probably better to reserve that as a once in a lifetime experience. Texas has three cool areas to play, all in Big Bend: Closed Canyon which is the only public slot canyon, Lower Burro pour-off which appears as if a volcano was cut in half, and the enormous Santa Elena Canyon. I hiked up the Rio Grande into Santa Elena about a half mile and found a ledge I could climb about 20ft. above the water. This turned out to be the ideal location for playing flute, it was as if I was playing in the largest cathedral in the world with a somewhat long delay and a not so long reverb decay, great for playing slower passages, UPDATE: I went back in November 2022 to discover the Rio Grande had flooded (rare event) which changed the acoustics greatly, I found an incredibly rich reverb while playing and had several folks tell me that it was the highlight of their day to hear me play in the canyon! How very nice to hear these comments from complete strangers. Every natural space I have the opportunity to play gives me the feel of "Natural Surround Sound" as it were. I'm always looking for nice acoustics so If y'all know of any other places lemme know!