A walker on the desert, far far away. Beneath a vast underground chamber, entirely composed of shifting, fragile sand, with no solid rock structures to anchor the structure. Its lofty, boundless expanse is shrouded in swirling sand-laden mist, which merges with the darkness; even the few vertical features here are not rock, but tall, unstable sand pillars, eroded by underground drafts, their edges soft and crumbling. Beneath is an expansive sea of loose sand. A single underground river cuts a winding path through the loose sand: it meanders from near the foreground to the distant, indistinct horizon, its surface emitting a faint, cool green glow, light that only casts a narrow, trembling sheen over the water and a tiny strip of damp, soft sand along its crumbling banks. There are faint, scattered fluorescent pinpricks glowing dimly. High resolution, with detailed textures, cinematic lighting, and a cinematic composition, hyper-realistic. In the style of the movie "Dune", the texture of CG films, realistic future science fiction style. Ultra-realistic.