The interesting thing which relate the canyon to the Hollow Earth theory is that the locals say there´s a waterfall with a hidden cavern behind. Allegedly, this cavern goes hundreds and hundreds of miles deep into the inner surface of the Earth. It leads all the way through the Earth´s shell but as one adventurer reported, the passage is sealed by a great metal door several miles below. This may sound as if it have been taken out a fantasy movie but is a possibility since it´s not the first time that local myths or legends turn out to be truth. Also the myth of Shangri-la, as described by James Hilton's in his novel "Lost Horizons (1933)", is believed to have been inspired by the Tsangpo Gorge. And more interesting yet is the fact that from time to time, the different lamas journey down this cavern and knock on the metal door, hoping someday an emissary will emerge to help establish world peace as foretold in their profecies. Awesome!
In other hand, in 2009 China began plans of constructing a dam which will damage the ecology and geography of that place. As I mentioned on the post < New albatross specie >, there are so many unexplored things in this World (or things hidden to general population), is a shame we´re destroying them before knowing all its secrets.
If you want to do some research on your own. Look for the city of Agharta.