A professional, epic book cover for Clive Cussler's "Regatul" audiobook. Visual style: realistic with a touch of atmospheric mystery, reminiscent of adventure and historical fiction thrillers. Main imagery: a submerged ancient city, partially revealed by shafts of ethereal light piercing the deep blue ocean water. Scattered around are hints of advanced, lost technology or ornate architecture. A lone, stylized nautical symbol (like an ancient compass rose or a crest) subtly integrated into the debris or the light. Color palette: deep blues, aquamarines, and dark greens for the ocean, contrasted with glowing golden or ethereal white light. Mood: mysterious, ancient, powerful, and slightly ominous. Composition: The submerged city should be the focal point, with the light creating dramatic highlights. The title "Regatul" prominently displayed in a bold, antique-inspired font, perhaps with a subtle metallic sheen. The author's name, Clive Cussler, positioned below the title. Atmosphere: a sense of immense depth and undiscovered secrets. Aspect ratio: 1024x1024.