A colossal subterranean megacity carved into a massive crystalline cave system beneath a forgotten mountain range, towering mineral spires with internal phosphorescent mineral veins illuminating vast underground chambers, suspended glass elevator districts connecting glowing fungal biodomes, sleek subterranean craft gliding through underground river networks, sky gardens with bioluminescent moss cascading over crystalline terraces, deep obsidian and electric teal palette with soft mineral glow filtering through translucent cave walls, epic upward shot from central underground plaza with tiny silhouetted miners on illuminated observation platforms emphasizes impossible subterranean engineering scale, photorealistic, cinematic depth of field