@vicgrinberg Usually the conversation pivots pretty quickly to "do you also have these issues with it?"

@geoff_eg I like your #alttext but it's not really descriptive / helpful for the visually impaired.

Maybe something along those lines could work:
"A photo of a narrow mountain valley. The left and right sides of the picture are framed with steep cliffs. In the middle of the image the end of the valley can be seen. It's a greenish steep rockwall. While the cliffs left and right go fairly straight up the rockwall in the middle tilts right at a 45° angle"