Underground Thermal Baths

A photorealistic render of the main bathing hall of a contemporary underground thermal bath complex built beneath a historic town square in northern Italy, the new structure entirely subterranean with access by a glass-enclosed lift and staircase from the piazza above. Main pool hall: An elliptical space approximately 30m x 18m, entirely below grade at 8m depth. The ceiling is a shallow elliptical concrete vault (maximum 5m height at apex, 200mm shell thickness) perforated by a grid of 48 circular oculi (each 600mm diameter) that pass through the full depth of the historic paving above — each oculus glazed with a clear acrylic lens at pavement level, admitting a precise column of natural light into the bath hall below. The oculi are arranged in a regular 2m grid across the vault, creating a field of light columns that move slowly across the water surface during the day. Water: The main thermal pool (elliptical, 22m x 12m, depth graduated from 900mm to 1600mm) is lined in small-format mosaic tile (25mm x 25mm) in a deep sea-green (Bisazza 24.07), the color shifting from deep teal in the shallows to near-black in the deep zone. The thermal water (natural temperature 38°C) produces a gentle continuous steam that fills the space at head height and above, the steam backlit by the oculi creating shifting light volumes. The water surface is barely disturbed, with only the slow movement of bathers. Walls: The perimeter walls of the ellipse are cast in-situ concrete (smooth formwork, white Portland cement with white aggregate, creating a near-white surface), the curvature perfect and uninterrupted. A single continuous bench in honed white Carrara marble (600mm wide x 500mm tall) follows the full perimeter at water's edge, its surface polished smooth and slightly warm from the radiant floor heating in the marble. Light quality: The combination of the 48 light columns from the oculi above and the underwater LED lighting (set to a very deep warm blue, 430nm, at low intensity) creates an extraordinary layered light environment — columns of cool natural daylight from above meeting warm blue underwater glow from below, the steam making all light sources visible as volumetric shafts and glows. Bathers: Eight to ten figures in the water and on the marble bench — some standing in the columns of light, the water at waist height; others seated on the bench; all in neutral swimwear that does not distract from the architectural atmosphere. Camera angle: From the water's edge at one end of the ellipse looking along the long axis toward the far curved wall, the field of light columns from the oculi creating a forest of light across the steam-filled space, the pool surface a dark mirror below. Focal length equivalent 28mm. Aspect ratio 16:9. Time of day: 11:00 AM, spring equinox, light columns at maximum intensity.