It is a gigantic reservoir 70 m long, 25.50 m large, 15 m high, which derives its name from the eighteenth century antiquarian tradition, with clear reference to the impressiveness of its plan. It is dug in a tufa hill and has two step entrances in the north-west and south-east corners, this latter closed. Forty-eight pillars, arranged on four rows serving as a support to the barrel vault, divide it in five aisles on the long sides and thirteen aisles on the short sides, lending to it the majestic look of a cathedral.
The reservoir was built in the Augustan age in order to convey the waters of the Roman aqueduct of the river Serino, which flew into it near the north-west entrance. This dating is confirmed by the building technique of the long walls, in opus reticolatum (reticular work) with brick bonding courses and by the technique of the tufa stone pillars, both covered with a thick waterproof layer of opus signinum (pounded terracotta). The seventh short aisle, just in the middle of the reservoir, appears embeded in it for about 1 m, with the plane inclined in the direction of an outlet at the south end. It was used as a Piscina limaria for the periodical cleaning of the reservoir.
The water, through a series of doors opening in the vault along the central nave, was raised through hydraulic engines on the covering terrace of the reservoir, which was also floored with signinum and from there, canalized towards the built-up area.
It has been assessed that it could contain 12,600 cubic metres of water. probably such quantity provided sufficent waterfor the military base of Miseno. Along the north-west external side, in the course of the first century A.D. were added twelve vault-covered little rooms in opus reticolatum with angular brick bonding courses, in the second of which is kept a signinum floor with labyrinth-sbaped mosaic tesserae and a central white inlaid panel with limestone polychrome tiles, which seems to date back to a more ancient phase
 

 Last updated 02/06/2004 13.58