Spectral Orb Over an Underground City

A highly detailed 3D render of a luminous spirit orb floating above an expansive underground city. The orb is translucent with iridescent blue-green hues, softly crackling with inner light, and features subtle fractal patterns. It casts a warm, volumetric glow that reveals damp stone arches, ancient carvings, stalactites, rusted pipes, and cobblestone streets lined with bioluminescent fungi. In the distance, a subterranean skyline of carved towers and bridges fades into mist. Cinematic lighting, volumetric fog, realistic reflections on wet surfaces, and depth of field create a moody, otherworldly atmosphere. Emphasize photorealism, subsurface scattering in the orb, ambient occlusion, and high-detail textures.