Piscina Mirabilis
The Piscina Mirabilis (Latin "wondrous pool") is an ancient Roman cistern on the Bacoli hill at the western end of the Gulf of Naples, southern Italy. It was one of the largest ancient cisterns. It was built under Augustus as suggested by the building technique of "opus reticulatum" used in the walls. The cistern was dug entirely out of the tuff hill and was high, long, and wide. The capacity was . It was supported by vaulted ceilings and a total of 48 pillars. It was thought to be situated there in order to provide the Roman western imperial  fleet at Portus Julius with drinking water but this is unlikely, as the cistern is about 1 km away from the slopes of the promontory of Misenum where the military base and residential area port were located. Also from the Augustan period, the naval base was directly connected to the main Roman aqueduct, the Aqua Augusta, and did not need the cistern. More likely is that the cistern belonged to one of the many luxurious villas built in this area, like the nearby Grotta della Dragonara cistern. The cistern was supplied with water from the Aqua Augusta, which brought water  to most of the sites around Naples from sources in Serino near Avellino, 100 kilometres away. Water was pumped out of the cistern using machines placed on the roof terrace of the cistern, which were increased in the 2nd c. AD by adding a series of supporting barrel-vaulted rooms on the north side. The ancient cistern is currently in private hands, but it may be visited by the public.