As night falls over the slopes of the Cerro Gordo, the kaleidoscope of colours from yellow to black should be a delight for a photographer. But the stunning natural beauty of the site in southern Mexico conceals a horrific hidden truth. "The majestic mountain is a mass grave", writes AFP photographer Yuri Cortez, "a dumping ground for dozens -- if not hundreds -- of people fallen victim to the hellish violence of the Mexican drug trade."