Hmmmmm...Unidentified Earth 21 is still unidentified. Here's a hint: I cut the notable feature of this location in half for the image used in the original post.
Also, Unidentified Earth 20 has been identified -- actually this happened last week, and I was remiss in noting it. It is the ancient city of Petra, located in present-day Jordan. In the second hint, I noted that part of the Unidentified Earth location, but not the part I used for the puzzler, was used in a famous movie, but as a totally different location. The film is Indiana Jones and the Last Crusade, wherein the most famous part of Petra -- the buildings carved directly out of solid cliff face -- are said to be the lost Temple in the Canyon of the Crescent Moon, wherein lies the final resting place of the Holy Grail.
The winner? Shawn, who now earns ten thousand Quatloos.
A new puzzle will run on Thursday.