The Piscina Mirabilis

The Romans built a large cistern connected to the Serino aqueduct, providing an abundant fresh water reserve sufficient for the needs of the ships and the garrison in the Misenian basin. It is an immense rectangular tank excavated in the tufo bank 70 metres long, 25.50 wide and 15 metres deep. The vault is supported by arches and 48 huge rectangular pilasters arranged in four rows. It is lined with a thick layer of “pounded terracotta”, regarded to this day as an excellent hydraulic cement for lining cisterns; a hard thick crust of calcareous sediment from the Serino water can still be seen. This water entered it on the east side and as there is apparently no other opening, it must have been raised by means of water-weels up to the terrace and thence conducted to a large tank built at the foot of the hill on the left side of the port of Misenum, probably in a place called “Case Vecchie” as some ruins show. The water then was put in amphoras, water-skins or other containers, loaded on boats and transported to the ships in the port.
The cracks and crevices here and there in the roof produce a strange play of light and shadow; clumps of plants and long sprays of ivy border the crannies or hang down through them, and in the damp penumbra of the aisles those azure rents and tufts of luminous green give one the sensation of being and moving in water.