Ginormous canyon complex north of Green River, UT?

Most of the Tavaputs Plateau and Book Cliffs in that area are difficult to get into and remote. Desolation and Gray Cyns are accessed by river. Nine Mile is famous and easy to drive through and see, most do it from the Price end.

I've flown over and explored some of that country and believe me, it's canyon after canyon with knife-ridged tops. There's a reason it's not well-known. Get Redtail Aviation out of Price/Moab to take you flightseeing, it's cool country.