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An ancient Roman urban Cistern that was, most likely, for more than a century, the biggest one in the world.

If Pasquale Mattei hadn’t been the first to speak about it in 1860, having collected many testimonies of Castellone’s citizens who went in the Cistern, I wouldn’t probably be here writing this post now.

After Pasquale Mattei, Formia’s Podestà Felice Tonetti, in 1930s, climbed down more than ten metres below the foundations of Castellone’s buildings to see the monumental Cistern now called Cisternone.

Not many people know that when these two events happened, what is now the Cisternone’s slab, it was so overlooked by the same buildings as today plus other eleven (some of them very big) destroyed by allies’ bombardments in May 1944. That’s the way that Piazza Castello was born.

The complication of penetration and exploration of the cistern at the time of Mattei and Tonetti, in a labyrinth of buildings, were more superior than the complications experienced during the emptying and cleaning works which took place fifteen years ago.

In this way, we were able to know the unusual shape of the underground artifact that Formia we like to believe that it was one of Marco Vitruvio Pollione’s projects, who was considered the main expert of plumbing structures.

His sizes:

Mq 1.200 – height mt 7,5. – capacity MC 7.000 – longest side mt 64,90. – width mx mt 25. – 53 pillars for three naves plus other 36 pillars against the perimetral walls. Its function seems to have lasted at least until the middle of 1800 and it was probably used also to feed the smaller bourbon cistern in S. Teresa square, of about mq 250.

The fact that this structure was projected underground springs from a technical reason. The underground cisterns are obviously more adequate to substain the lateral pushes of a big mass of water that in this case is 7.000 cubic metres.

They compare this structure and other similiar two and it’s said that our cistern is the most ancient and the third in the world after the cistern of Yerbatan in Istanbul and Piscina Mirabile of Bacoli in Miseno.

The dimensional and architectural comparison with three monumental cisterns of Yerbetan built in 5th AD (600 years of temporal distance from Formia’s structure) has no sense.

It’s a comparison between the structure realized in a small city and another built in the Oriental Capital of an empire which covered the biggest part of the western world of that time.

It’s interesting in the comparison with Piscina Mirabile of Bacoli, because it has an historical bond which convects the Sinus Formianus with Golfo Miseno.

Piscina Mirabile was built in 1 century AD, when the Tyrrhenian Roman fleet, at the decision of Augustus in the first years of his empire, was moved from Sinus Formianus to the Miseno territory, thinking to reach safe docks in Averno and Lucrino’s lakes.

This transfer was gradual, it took about a century untili t ended tragically for 200 ships destroyed by a sea storm while they were moving from Formia to Miseno in 62 AD during Nerone’s empire, how Tacito and Strabone said.

The graduality of the transfer was due to the harbour works to do, to the construction of the underground cistern (now called Piscina Mirabile) and to the difficult construction of the aqueduct, which is 100 km long, partly outdoor and partly underground, to pick up Serino’s water and carry i tinto Bacoli’s cistern.

This cistern was built with evoluted systems based on the Formia’s cistern prototype.

Its sizes are: height of cruciform section pillars 15 mt – rectangular shape long side 70 mt and short side 25 mt – capacity 12.000 MC.

The perimetral dimensions are as long as Formia’s ones, but with a higher and easier implementation as it is dug into the tuff.

So, our cistern, which is the most ancient of the three, for more than a century was one of the biggest roman urban cistern in the world or maybe the biggest one.

This historical fact amazes a lot of people, but it’s the truth. Most of them will wonder why a colossal construction was built in Formia. Obviously, it serves as a supply to give water to the many domus built by a rich and noble Romans.

But I think that its most important public function was the hydro supply for the Tyrrhenian Roman fleet, which stopped in the Sinus Formianus until 62 AD as it was necessary to build another of the same dimensions in Bacoli.

The historical nexus, that connects Formia to Miseno, stands both for Roman fleet’s placement, trasferred from Formia to Miseno until Diocleziano’s ages, and for roman world AD, whereas naval fleet was deplaced, it had certainly to be a big cistern like the Cisternone and Piscina Mirabile.

How romans built such a big underground plumbing structure, still remains a mystery to discover.

Considering the slub, the foundations and the perimetral walls thickness, we can understand that it was necessary to pull out from a hole 15 metres deep, 20.000 mc of material from Castellone’s Arce, which stands 58 metres above the sea level.

It’s also a mystery where this huge mass of material has been moved.


Raffaele Capolino


CURIOSITA’ dall’Autore

QUELLA VOLTA CHE IO E QUINTINO (il papà di Augusto Ciccolella) SCENDEMMO NEL CISTERNONE ROMANO DI CASTELLONE – continua lettura cliccando qui




Stories and related hypothesis.

It’s represented in the photo. That’s a photo I had to take with my mobile phone because it’s an architectural element of the Cisternone that is rarely photographed. The photographic result is obviously lower than the photos taken by professionists.

And yet this “small arch” must have had an important function in this Roman hydraulic structure that has arrived at us intact in all of its structural parts, even if with absent particulars that makes different from similiar structures.

For example the Cisternone has no covering in “cocciopesto” on the walls and on the pillars. The cocciopesto is a waterproofing typical element of every roman hydraulic structure. A lot of visitors notice this absent detail, the builder have had used a good quality of hyidraulic mortar for elevate the thick perimeter walls and the over eight central and walls pillars.

It was supposed for example an “hydraulic charge” coming from a waterway in S. Maria La Noce but no channeling was found. It must have been lost in the course of public and private refurbishments that have interested the Arce in Castellone in the two millenials this cistern that is situated at about 60 metres from the sea level. At the primary source, as supply, it was surely added the rain-fed one through the several holes in the covering.

Neither water outlet holes have been found, not an inclined level with a “limaria” pool needed for the cleaning works of the big reservoir extendend for about 1200 mq.

All these absents characteristics have been found in the Mirabilis pool of Baial made a few centuries after the Formia one.

Let’s return at the small arch of the first photo with less of two palms widths. In its inside it can be seen a space less than a square meter.

It seems to have all the characteristics of a “well” created for the loading coming from the hilly source. The narrow space between the shoulders of the sufficiently allowed the immediate distribution of the entered liquid.

About the distribution system it was maybe expected a lifting system like a “suction pump of Ctesibio” mentioned by Vitruvio in his treaty. (Ctesibio also invented the water organ and the water clock).

The levy took place through the holes in similiarly to what was done in the Mirabilis pool of Baia al Miseno.

Surely beside the big storage of Castellone there must have been different “castles” of distribution that let an easier management of the liquid masses.

Checking the outflow of 10.000/20.000 litres was of course easier to handle 7.000.000 of litres corresponding at the highest level of filling the hydraulic structure we are talking about.

Anyway there must be at least an exit hole, definitely placed at the floor level and on the left side of the inside masonry staircase with an outlet in the Carbon garden underneath, railroad side to fall out in the current Mamurra street. This hole was needed for the cleaning operations of the Cistern.

Another interesting historic particular is that Sesto Giulio Frontino (40 – 104 d.C.) metioned in the 95 from the emperor Nerva “Curator Aquarum” of all the aqueduct of Rome, had a manor in Formiae. In one of his scripts by Eliano Tacticus that he met the emperor Nerva in his house of Frontino in Formiae.

In that occasion the emperor Nerva committed to Eliano Tactitus the charge of writing work with military character (Strategamata) on the Greek phalanges. Eliano Tacticus wrote “I could have spent some days in Formia with the consul Frontino, remarkable man of a big reputation, for his qualities and his war experience”.

So Frontino left Rome often to enjoy the climate and the beauties of Formia showed off from Marziale.

Frontino, therefore, must have definitely known and visited our cistern making his experiences as Curator Aquarium of the “Caput Mundi”.

In the end I believe very likely that the structure of the Cistern hasn’t been created for the privates domus equipped of “impluvium” and supplied from the several minor sources, but for the public thermal baths, to supply the ships in the “Sinus Formianus” and for the needs determined by the presence on the arce of a militar “Castrum” born to protect and to control the transit of people on the Appia way.

I hope it will be born an heated debate with others and more appropriate hypothesis that could help to expand our present and poor knowledge about this hydraulic  Roman structure that was a prototype of bigger ones made in the subsequent centuries.


Raffaele Capolino.


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