Going down the fifty-two steps of the Great Cistern buried in the middle of today’s Istanbul, a true time machine effect occurs. An enchanted forest of towering stone columns with their reflections in a sheet of water materializes before our eyes: we are in an immense underground lake space, in the middle of the 6th century AD, in Constantinople, the New Rome of Emperor Justinian.

At the beginning of the 20th century, the Irish poet and playwright William Butler Yeats, a great admirer of Byzantium, said, “I think that if I were offered a month in Antiquity free to spend where I wanted, I would spend it in Byzantium, a little before Justinian opened Hagia Sophia and close Plato’s Academy…”. The chosen moment is truly splendid for many reasons: after some hectic times, the porticoes of the city were once again full of life, as were the schools, the libraries, the stoa… The joyous noise of the water in the aqueducts, public fountains and hot springs. This was the area in which the Great Cistern was created, Yerebatan Sarayi as the Ottomans would later call it, the Underground Palace.

Just like the Pantheon in Rome from the 1st century B.C. Still having the largest known dome with its diameter of 43.5 m, the Hagia Sophia in Constantinople, built six centuries later in the New Rome, is undoubtedly the largest construction of Antiquity and of the ten centuries that have followed its construction. The elegance of its structure, the light it provides inside, the refinement of its decoration and all its details… its qualities are overwhelming. Hagia Sophia –Holy Wisdom, Sancta Sapientia in Latin– was built between 532 and 537; the realization honors her name. The immense dome is designed to produce a sound

Only a few days after having conquered the city in 1453, Mehmet II decided to use it as a mosque –Hagia Sofia (in 1930 Atatürk secularized it, but since 2020 it is working again as a mosque)–. All the imperial mosques that have been built since have used the same volumetric concept, with a hemispherical dome supported by half-domes resting on two parallel resistance walls.

The Great Cistern is found –hidden– right in front of the great basilica, its construction has been carried out in parallel with that of Hagia Sophia. Yeats would have been able to see her if his wish had come true, benefiting from some inside information. The endless number of monolithic columns is simply amazing. They are eight meters high, they are made of different varieties of marble and granite, their capitals can be Doric, Corinthian, simple or compound; all these columns –very beautiful– are brought from other places in the empire and reused with impressive elegance. This way of recycling – quite common in the history of humanity – is known under the name of spolia. Here it is possible that pieces brought from far away have been used for the great work of Santa Sofia.

In a perimeter that measures 135×65 meters, twelve rows of 28 columns have been arranged, 336 in total, spaced approximately five meters apart. The ceiling is made of small interlocking brick vaults supported by circular arches. The enclosure is defined by thick brick walls four meters high and protected by a waterproof coating: it can store a volume of 78,000 m3 of water. Fischer von Erlach, the prestigious architect of the Karlskirche in Vienna, has included the drawing of the section of the Basilica Cistern in his compendium Plan for civil and historical architecture published in 1737, which groups together “the most outstanding constructions of foreign nations, both ancient and modern. It seems that this underground cistern was just as fascinating to him then as it is to us now.

To better understand the circumstances that have led to such a unique work, we must go back two centuries before, think about the premises of the founding of this great metropolis of Antiquity, and the personal history of Constantine I, the emperor who has promoted this reorganization. radical of the Roman Empire. Diocletian, who ruled before, had already expressed the idea that the empire has grown too large to be ruled by one man from a single center of power. He had decided to divide it into four parts, naming four Caesars, one of whom was himself and the other the father of Constantine. Upon the death of the old emperor, in the fierce struggle for power between these heirs, Constantine finally prevailed as sole emperor, reunifying the empire.

Straight away, as an astute soldier and a good diplomat, he has assessed that Rome was too dangerous in that context of political instability and incessant external attacks. He has decided to move his headquarters to Byzantium, a small and ancient Greek colony on the European side of the Bosphorus Strait; It was the city of King Byzas, already mentioned by Diodorus in his account of the Argonauts. Apart from its strategic position controlling access to the Black Sea, the new capital – renamed Constantinople in AD 330 – was to be built on an easily defended peninsula, and had an excellent natural harbour, the Golden Horn.

Constantine’s spiritual life is also highly significant for the course of his empire’s history. He already had a sensibility for Christianity, which had been heightened in the turbulent years preceding the victory over his rivals and in his first years as emperor. In 312 he has officially converted to the Christian religion (he has been emperor from 306 to 337 AD). Progressively, Christianity has become the official religion, producing a church-state fusion: a major turning point in the history of the Roman Empire.

Constantine has ordered the reconstruction and extension of the walls, the construction of several churches –among others, one on which Hagia Sophia was later built–, an extensive hippodrome that would center an intense social life and many other works. The lack of water in the peninsula has determined him to order the construction of the most extensive system of viaducts in the Roman Empire; the sources were in the nearby woods. Thinking of the rainless summer months, and also of the possible long sieges that the city could suffer, he ordered the construction of various covered and uncovered cisterns to store water.

In its first phase, especially, in the Eastern Roman Empire, a form of solidarity could be perceived in which being a citizen – rich and poor – meant enjoying privileges and comforts.

Years later, Theodosius I –born in Hispania, the last emperor to rule over the two halves of the empire, the Eastern and the Western (which later ceased to exist)– made Christianity the only accepted religion, persecuting pagan beliefs. The construction of public works has continued at a sustained pace. Two smaller underground cisterns from the mid-5th century AD still remain: Philoxene’s and Theodosius II’s. They are one of the few precedents that can be related today to the Basilica Cistern. Later, Justinian – who was emperor between 527 and 565 – defied various conventions, adapting the empire to the new times and, at the same time, defending the extensive cultural heritage of his New Rome. Nobody talked about Byzantium at that time – the term in its modern meaning is an invention of the Renaissance, which has been imposed in a lasting way: Byzantine empire, Byzantine culture, Byzantine character…–.

A difficult question to answer is why the Basilica Cistern is so beautiful, being merely a functional space that was not meant to be seen. Some say that the Romans did not know how to make ugly; others invoke rudiments of spiritual concepts – and it is possible that this last possibility could explain some strange presences that are found there. Two columns have sculptures at their base with different representations of the Medusa, which is an apotropaic motif, that is, its function is to ward off evil spirits. The Medusa is a monstrous female spirit from Greek mythology who turns those who meet her gaze to stone. The belief is that having her on her side drives away evil; Pindar and Ovidio also saw her as pretty. On the other hand, the simple representation of the eyes can have similar functions, and here is a splendid column with the tears of Theodosius not far from the Medusas. Even transformed into decorative presences, these apotropaic elements retain some of their initial strength, the intention is present.

Yeats celebrated the knowing beauty of that moment in his 1928 poem Sailing to Byzantium: “…there are no schools of song but to study / The monuments of your own magnificence;/ and for this I have sailed the seas and come / to the holy city of Byzantium…”

A mysterious work, the Basilica Cistern proves once again that Byzantium –as a new culture– was born wise, having inherited and regenerated so much from previous cultures.