An immense underwater steampunk observatory rests on the ocean floor, its architecture built from riveted brass, weathered copper, dark iron, and thick glass. No living beings appear. Center the composition on a towering pressure dome with circular portholes, intricate gearwork, exposed pipes, and a slowly turning mechanical astrolabe, surrounded by smaller domed laboratories linked by transparent tunnels. A colossal brass telescope extends from the central structure toward the open sea, its lens catching a faint turquoise glow. Kelp-like copper cables, anchor chains, and delicate mechanical instruments sway gently in the currents, while tiny bubbles drift upward. Frame the scene as a cinematic wide shot from a slightly low, three-quarter perspective, emphasizing the observatory’s scale against the vast, dim seafloor. Layered blue-green water fades into deep navy distance; shafts of filtered light descend from the surface, glinting across metal edges and illuminating suspended particles. Warm amber lamps glow behind fogged glass, contrasting with cool aquatic shadows. Add scattered rocks, pale coral formations, and an old half-buried compass for scale. Rich patina, oxidation, condensation, scratches, and realistic glass refraction create tactile detail. The atmosphere is mysterious, quiet, and contemplative, blending Victorian industrial design, nautical fantasy, and cinematic steampunk illustration.