The Somnia Chronicles Notes

Episode 3 · Notes

Why Was the Basilica Cistern Built? Water in Justinian's Constantinople

Constantinople had no great river. The Basilica Cistern was built under Justinian to store water for the dry summers. What the sources say, and where they disagree.

Episode 3 coverWatch the episode · about two hours

The short answer: the Basilica Cistern was built to hold water for the summer. Constantinople had no great river, and in the dry months its springs ran low. Water reached the city along channels hundreds of kilometres long, and cisterns stored it for the months when there was not enough. Procopius, writing in the reign of Justinian, says the emperor had a great courtyard dug out to make a store for the summer, so that, in his words, "the people of Byzantium should not be in want of fresh water."

Why did Constantinople need cisterns at all?

Many great ancient cities grew up beside a river. Constantinople did not. The archaeologist James Crow, who has spent years tracing its water supply, puts it simply: the city was not built on a major river.

So the water was brought in. An old aqueduct dated back to the time of Hadrian, long before the city was Constantine's. In the fourth century, much longer channels were built from springs out in Thrace. By 373 the first great line was complete: more than two hundred and fifty kilometres of channel, crossing around a hundred and thirty bridges. From around 400, the builders went further still, to springs nearly a hundred and thirty kilometres from the city. Altogether the channels ran for hundreds of kilometres. Scholars give different totals, so we will not pick one.

You can still see part of it today. The aqueduct of Valens, nearly a kilometre long, carries the channel from one of the city's hills to the next.

But an aqueduct only delivers what the springs give, and in summer they gave less. That is where the cisterns come in: great open reservoirs at the edge of the city, and covered ones under its streets. A list of the city's buildings from the fifth century counts four cisterns. Crow cites recent work that has documented around a hundred and sixty, and notes that this is probably only a small part of how many there once were.

What do the sources from Justinian's time say?

Two writers of the sixth century mention it.

Procopius, in his book Buildings, explains that in summer the city suffered from a shortage of water. He then describes a very large courtyard at the Imperial Portico, "where the lawyers and prosecutors prepare their cases", with a colonnade on each of its four sides. Justinian, he says, had the courtyard and the colonnade facing south dug out "to a great depth" and made into a storage reservoir for the summer. When the aqueduct brought more water than the city could use, the overflow went into the store. When water ran short, it supplied those who needed it.

The chronicler John Malalas, also writing in Justinian's lifetime, gives a different detail. He says Justinian built the central hall of "the Basilican cistern", intending to bring the water of Hadrian's aqueduct into it.

Two cautions. Buildings was written to praise Justinian, so its picture of the emperor caring for his people is not neutral. And neither writer gives the year the work was finished.

Where does the name come from?

The name is old. Malalas already calls it the Basilican cistern, after the great public building above it, the Basilica, whose courtyard was dug out to make it. Today, in Turkish, it is called Yerebatan.

When was the Basilica Cistern built?

The short answer is: in the early years of Justinian's reign, which began in 527, and perhaps not finished until around 541. The exact years are not certain.

You will often see 532 given as the date. We could not find an ancient source for that year. The chronicler Theophanes, writing around 814, records the work among the events of Justinian's first years. Malalas also places it in Justinian's reign, and records that in 541 or 542 the city prefect Longinus paved the central hall of the cistern, which modern scholars read as work on the courtyard above it. Crow and his colleagues put it carefully: if the work began in 526, the project was possibly not completed until 541. Crow also groups this cistern with the one now called Binbirdirek: the two largest covered cisterns of the city, both from the reigns of Anastasius and Justinian, roughly the late fifth to the mid-sixth century.

Some later writers got it wrong. A collection of notes on the city's monuments from the eighth century, and another from the tenth, credit the cistern to Constantine the Great, two centuries too early. An eleventh-century chronicler, Kedrenos, gives it back to Justinian.

What was it used for?

It was a reserve: a store, filled by the aqueduct when the water ran plentifully, for the months when there was not enough.

Water mattered enough to appear in the empire's laws. Justinian's law book of 534 kept older laws about the aqueducts, still in force in his reign. Under one, landowners along a channel were spared certain extra burdens but had to keep the channel clean, and no tree could grow within fifteen feet of it. Another punished anyone who tapped the water in secret to irrigate a field or garden. One law, from the emperor Theodosius II, says it would be abominable for the households of this city to have to buy their water. Crow took that line as the title of one of his studies.

A law of the emperor Zeno, kept in the same book, names the men who guarded the aqueducts that fed the city's water: the hydrophylakes, the water guards. The law says each guard was to have the emperor's name marked on his hand, so that he could not be taken for other work. Whether that rule was actually carried out, how many guards there were, and how their nights were organised, the sources do not tell us.

How big is it?

The roof rests on three hundred and thirty-six marble columns, in twelve rows of twenty-eight. That is the count a French scholar made in the sixteenth century, and it is the number the cistern is known for today.

The columns are not all alike. The same scholar noted that some of the capitals were finished in the Corinthian style and others were left unfinished. Crow observes the same thing across the city's cisterns: some capitals were reused from older buildings, and others came from the marble quarries of Proconnesus, some of them finished and some not.

How was it found again?

By the sixteenth century, people living above it drew water from wells in their own houses without knowing what lay underneath. In the 1540s the French scholar Pierre Gilles (Petrus Gyllius in Latin) came upon it. He tells us he went down into it from one of those houses and was taken out in a small boat. The owner lit a torch and rowed him between the columns. The owner also speared fish there. Gilles noticed that the fish came up to the light falling through the well openings, to breathe.

He counted the columns, three hundred and thirty-six in twelve rows of twenty-eight, and noted that in winter the water poured in noisily through a large pipe. He also claimed that he was the first to find it. That is his claim, and we repeat it as his.

What happened to the water supply later?

The system was fragile. In a siege early in the seventh century, the aqueduct of Valens was cut, and it was not repaired for well over a century, until 765.

Listen to it as a story

Our third episode imagines one summer night in Justinian's city. A water guard we invented walks the channels at dusk. We go down into the cistern we now call the Basilica Cistern, pass a bakery at midnight, and reach home at dawn. It is about two hours long, told slowly, and made to fall asleep to.

Watch "Fall Asleep to the Basilica Cistern, Constantinople, 6th Century" on YouTube

Sources

Further reading (not read for this note): James Crow, "Water and Late Antique Constantinople: 'It would be abominable for the inhabitants of this Beautiful City to be compelled to purchase water'", in L. Grig and G. Kelly (eds), Two Romes (Oxford, 2012), pp. 116–135 · J. Crow, J. Bardill and R. Bayliss, The Water Supply of Byzantine Constantinople (Society for the Promotion of Roman Studies, 2008).

Written from the research behind our sleep-history episodes. Spotted a mistake? Tell us in the comments on YouTube and we will fix it.