Each great metropolis should have its own grand avenue that would form not only the main axis of the transportation but also a space where great events and processions can be celebrated. It was also the case of ancient Constantinople with its Mese, from the Greek word "Middle". It connected the very centre of the city, starting at the Milion monument, the zero-mile marker for the East Roman Empire, very close to Hagia Sophia. The Mese then followed in a perfectly straight line in the westward direction, connecting the main forums of the city, first the Forum of Constantine, next to the Forum of Theodosius, and then branching off in two directions.

The first of these branches passed the Church of the Holy Apostles and reached the Gate of Polyandrion. The second one continued to the southwest, via the Forum of the Ox (Forum Bovis) and the Forum of Arcadius, to the Golden Gate, where it connected with Via Egnatia and continued to Thrace and the Balkans. Amazingly, the Mese is the only street from the Byzantine period of the city that has its route preserved in a stretch longer than some hundred meters. Today, the first part of this grand ancient avenue, up to the Forum of Constantine, is followed by the modern street called Divan Yolu. However, we are going to walk a bit further to the west, to investigate the faint traces of the Forum of Theodosius, located opposite the campus of Istanbul University in Beyazıt Square.

The history of the Forum of Theodosius area goes back to the times when the city was called Byzantium, and it had its own agora, possibly in the area called the Strategion. This agora, with Hellenistic origins, was later developed into a forum during Emperor Constantine, together with his eponymous forum along the Mese. Many monuments decorated this forum, including an equestrian statue of Constantine.

Some authors, such as Cyril Mango, believe that the Strategion was precisely the area later upgraded to the Forum of Theodosius. However, other researchers, such as Nigel Westbrook, are more careful, arguing that the exact site and size of the Strategion still has to be determined. Moreover, it is quite possible that there actually were two Strategia: the large one playing the role of a parade ground, and a small one - at the later Theodosius Forum, with the representational function, public monuments, and statues. On the other hand, it seems that there is a consensus that the Strategion was located in the later Theodosian Forum or its vicinity.

In this moment, it is worth mentioning that the centre of the ancient city of Byzantium was not located at the easternmost tip of the peninsula, where it would have been encompassed by the water on three sides. Instead, this settlement lay along the southern shore of the Golden Horn, at the foot of the hills, while the southern part of the city was not as densely settled. Thus, the area, now perceived as the heart of ancient Constantinople, i.e. the vicinity of Hagia Sophia, was established in an area that had previously been more or less empty. That gave Constantine ample space to develop the ambitious building programme for his new capital in the first half of the 4th century.

This also meant that when the city centre moved to that area, the main street - the Mese - had to be created to connect it with the previous centre near the Strategion. At the same time, the Strategion area was turned into Forum Tauri, meaning the Forum of the Bull. This name may have reflected the grandeur of the imperial vision of Constantine with his venture of creating a New Rome in the East. Bulls as symbols have, for a long time, been associated with leadership, power, and sanctity. Moreover, many scholars believed that Forum Tauri was an enormous square, possibly the largest public square in antiquity, and this name and its symbolism would fit nicely to its grand proportions.

However, the estimates that gave the dimensions of the Forum Tauri, and the later Forum of Theodosius, as around 450 by 300 meters have been greatly diminished over the last century of research. Such an enormous square would have been totally out of proportion in the densely built-over area of the city. Moreover, because of the lay of the land, it would not have had a level surface. Thus, over the years, the supposed dimensions of the forum have gradually been reduced. For instance, Cyril Mango in his publications gave a much more modest numbers of about 120 by 100 meters. Moreover, an even smaller size has been suggested recently, on the basis of archaeological excavations.

It is now time to move to the times of Emperor Theodosius I, also known as Theodosius the Great, who ruled from 379 to 395. Notably, he was the last emperor to rule over both the Eastern and the Western halves of the Roman Empire. He is also responsible for the decisions that effectively made the Nicene version of Christianity the official state church of the Empire. From the perspective of Constantinople, Theodosius made some significant changes in the cityscape.

While the Forum Tauri renamed and redecorated as the Forum of Theodosius, further discussed below, is now virtually non-existent, there is one characteristic structure that commemorates Theodosius until today. In 390, Theodosius oversaw the removal of the Thutmosis III Obelisk from Alexandria to Constantinople. The journey of this monument to Constantinople began much earlier, during the reign of Emperor Constantius II (337-361 CE) who had it and another obelisk transported along the river Nile to Alexandria to commemorate his ventennalia, i.e. twenty years on the throne in 357. The other obelisk was erected on the spina of the Circus Maximus in Rome in the autumn of that year, and is now known as the Lateran Obelisk. On the other hand, the obelisk that would become the obelisk of Theodosius remained in Alexandria until 390 when Theodosius I had it transported to Constantinople and put up on the spina of the Hippodrome there.

This structure, now known as the obelisk of Theodosius, was originally much higher, just like the Lateran Obelisk that reached 32 meters. However, its lower part was damaged in antiquity, probably during its transport or re-erection, and so the obelisk is today only about 19 meters high, or slightly more than 25 meters if the base is included. It still stands in the area of the Hippodrome - now called the Sultanahmet Square, in front of the iconic Blue Mosque. The marble pedestal of the obelisk has bas-reliefs that date back to the time of its re-erection in Constantinople. On one its faces, Theodosius is shown offering the crown of victory to the winner in the chariot races, with happy spectators, musicians, and dancers assisting in the ceremony. In the bottom right of this scene, there is also the water organ, the invention of Ctesibius from Alexandria.

Also, in the Theodosian period, the Mese obtained the function of Via Triumphalis, when two ceremonial fora - of Theodosius and Arcadius, his son and co-emperor, with their famous columns, triumphal arches, and statues - were created. Forum Tauri was then renamed and redecorated as the Forum of Theodosius. Emperor Theodosius rebuilt it using the Trajan's Forum in Rome as a model, and had it surrounded by civic buildings such as churches and baths, and decorated with a triumphal column at its centre, and a triumphal arch in his honour.

The reason why Theodosius wanted to copy Trajan's architectural ideas from Rome can be explained not only because Emperor Trajan was one of the most successful Roman emperors. There was also a deeper motivation, exemplified for instance in the oration made by Themistius, a statesman, rhetorician, and philosopher who flourished in the courts of the emperors of the second half of the 4th century. Surprisingly, he enjoyed the favour of many emperors despite the fact that he was not a Christian. Emperor Theodosius, a devout Christian, made Themistius the prefect of Constantinople in 384. Of Themistius' works, thirty-three orations have been preserved as well as his commentaries to Aristotle. In one of his orations, Themistius addressed Theodosius saying that his ancestor Trajan honoured Lusius [Quietus] and appointed him successor to his royal power.

Moreover, Theodosius was born in Hispania, quite possibly in the town of Italica - the birthplace of Emperor Trajan himself. Finally, Theodosius' father, a senior military office Flavius Theodosius or Theodosius the Elder, claimed the descent from the gens Julia through Gaius Julius Caesar's cousin Sextus Julius Caesar. All these facts strongly hinted at very ancient and distinguished ancestry of Theodosius' family and his new forum in Constantinople reflected his position and power.

One of the most remarkable monuments standing on the Theodosius Forum was the column erected in his honour. The construction works started in 386, but only in 393/4, one year before the death of Theodosius, the column was crowned with his bronze statue. This statue fell down during the earthquake of 480 and was replaced in 506 by the statue of Emperor Anastasius I Dicorus (two-pupiled as he had one eye black and one eye blue). The statue of Anastasius did not stay on the column for a long time, as it was most possibly destroyed already during riots in 512, together with other statues of Anastasius. Those riots erupted after Anastasius deposed the Patriarch of Chalcedon and replaced him with a Monophysite as the religious conflicts of the era had an impressive influence on common people.

The details of the Anastasius' statue were recorded by Malalas, a Greek chronicler from Antioch: "John [John the Paphlagonian, comes sacrarum largitionum i.e. the senior fiscal officials of the late Roman Empire] melted down the statues of the plateia of Constantinople, which the most sacred emperor Constantine had collected from every city as being the finest, and brought for the decoration and adornment of Constantinople. After melting these down, John made from them an exceedingly large statue of the emperor Anastasios, and placed this statue on the great column which stood unused in the place known as the forum Tauri. This column had previously held a statue of Theodosios the Great, but the statue alone had fallen during the earthquakes."

The Column of Theodosius itself was located on high ground, overlooking the Sea of Marmara and thus visible to all the travellers approaching Constantinople by sea. However, the exact location of the column within the Forum of Theodosius remains a subject of controversy because it has not been established by archaeological excavations. Possibly the best source that suggests its placement is an engraved view of the city made by Giovanni Andrea Vavassore. This artist created a fine view of Constantinople published in Venice in 1520, so after the Ottoman conquest. This picture shows the column enclosed within the precinct of the Old Ottoman Palace, now the area of Istanbul University. Thus, the column seems to have been located off-centre, in the part of the Theodosius Forum to the north of the Mese.

It is interesting to observe that the first Ottoman Palace in Constantinople was built in the area of the Theodosius Forum, echoing the older settlement of Byzantium. Only later, the sultans moved to the new Topkapı Palace closer to the Bosphorus. Topkapı was originally called the New Palace (Yeni Saray or Saray-ı Cedîd-i Âmire) to distinguish it from the Old Palace. Sadly, no traces remain from this first residence of the sultans in the city, now the site of Istanbul University in Beyazit Square.

When it comes to the Theodosius Column, one thing is certain: it was one of the most impressive monuments of the city, reaching around 40 to 50 meters in height. It was made of white marble, just as its predecessors in Rome - the columns of Trajan and Marcus Aurelius. The exterior of the column was decorated with reliefs, climbing to the top in a spiral band. Those reliefs depicted, again as the tradition demanded, military victories of the emperor. In this particular case, the main theme was the triumph over the Goths and the destruction of their settlements in the Balkans. The surviving fragments of the Theodosius Column depict mainly soldiers on the march and in battle, and some city fortifications. One exceptional fragment shows a soldier in a boat.

When Theodosius became the emperor in the East, in January of 379, he succeeded Emperor Valens who was defeated and killed in the Battle of Adrianople, fought against the Goths in August of 378. Thus, becoming the emperor in the wake of the catastrophic Roman defeat at Adrianople, Theodosius was forced to face this threat. As a matter of fact, the Gothic crisis was so dire that his co-Emperor Gratian relinquished control of the Illyrian provinces and retired to Trier in Gaul to let Theodosius operate without hindrance. Theodosius, seriously ill for the most of 379, was able to enter Constantinople only in November 380, having prevailed by offering highly favourable terms to the Gothic chiefs. In another Balkan campaign, in 386, Theodosius stopped the Gothic tribe of the Greuthungi from crossing the Danube.

The Theodosius Column, again like other monumental columns of this type, had an internal spiral staircase that allowed access the top. This staircase was used not only for technical reasons as it is said that a stylite monk dwelled on the column in the mid-Byzantine period. Stylites were Christian ascetics who lived on top of a column or a pillar. This particular idea was introduced by St. Simeon Stylites the Elder, who took up residence atop a column in Syria in 423 CE, and as improbable as it seems, the practise was later quite widespread. Simeon's disciple, Daniel, brought it to Constantinople, where he had a series of pillars with a platform on top built for him by Emperor Leo I. Thus, it is very probable that another stylite took up residence on the top of the Theodosius Column, with its grand dimensions and the empty space left after the statue of Anastasius had been brought down.

The column was also used for far less innocent purposes. During the violent times of the Fourth Crusade, Emperor Alexios V Doukas achieved power through a palace coup, killing his predecessors in the process. He held on to the throne for around two months only, as in April of 1204 the crusaders stormed the city. Alexios V fled the city in a fishing boat, in the direction of towards Thrace, on the night of the 12th of April. In this way, Alexios V and his companions reached Mosynopolis (Maximianopolis in Rhodope), occupied by the deposed emperor Alexios III Angelos and his followers. After an initial warm greeting, when Alexios III daughter was given to the newly arrived Alexios V as a wife, the father-in-law quickly changed his mind. He had Alexios V blinded and banished. Abandoned by his supporters, Alexios V was finally captured by the Latin army in November of the same year. On his return to Constantinople as a prisoner, he was tried by Baldwin I of Flanders, the first emperor of the Latin Empire of Constantinople, for treason against Alexios IV.

Such a spectacular process had to have a grand final. After the public trial, the condemned prisoner was executed in an innovative way as he was attached to a board and thrown to his death from the top of the Column of Theodosius. This rather extravagant show of power was aimed at the population of Constantinople because the Latin conquerors needed an aura of legitimacy and the execution of the man who murdered the last "legitimate emperor" was the means to achieve this goal.

The Theodosius Column lasted much longer than the Latin regime, and it survived the Ottoman conquest of 1453. The column was demolished in the early 16th century, and its fragments were built into the foundations of Beyazıt Hamam, erected around 1507 by Gülbahar Hatun, one of Beyazıt II's wives and mother of Selim I. Some remains of the ancient column are still visible there, on the external wall of this building. Other fragments discovered there were moved to the Istanbul Archaeological Museum. When looking for this building, it is worth remembering that it is locally known as the Patrona Halil Hamam, after a rebellious Albanian who worked as an attendant there when he was dismissed as a Janissary. He later went on to lead the 1730 uprising that ended the Tulip Period, but this is for another story. Beyazıt Hamam underwent a big renovation and reopened as a museum in 2015. More pieces of the Theodosius Column were discovered in 1973 when works were conducted on the University Library of Istanbul, and they are now also in the Istanbul Archaeological Museum.

The other surviving fragments of the Theodosian Forum belong to the triumphal Arch of Theodosius, erected of Proconnesian marble, that once formed one of the entrances to the forum. Which entrance it was remains debatable, because it is usually believed to have been the forum's western entrance. However, as a number of foundation walls have been found close to this arch, it is also possible that it actually formed the eastern entrance of an area. Thus, on the basis of the remains of the foundation walls discovered in the vicinity of the arch, the latest suggested dimensions of the forum are given as only 55 to 55 meters, with exedra to the north. The small size the public fora in Constantinople may be quite convincingly explained by their purely ceremonial function. The Hippodrome, on the other hand, played the political and entertainment roles of the public space within the city.

Forgotten for many centuries, the marble pieces of the Theodosius Arch were finally discovered during the rearrangements of Beyazit Square and Ordu Street, conducted between 1948 and 1961. Their recovery enabled the experimental virtual reconstruction of the structure's original appearance as the three-arched gateway. Today, these pieces, including the characteristic column fragments, can be seen on the southern side of Ordu Street, opposite the Beyazıt Hamam.

Other incredible finds discovered during the excavations of the Theodosius Forum belong to the much older times, before Constantine the Great. One of them is the tombstone of Aurelius Surus, who had been trumpeter of the First Legion Adiutrix in the late 2nd century CE. He served for 18 years, and his funerary monument was erected by his heir and fellow-trumpeter Septimius Vibianus. It is possible that Surus may have been killed during the siege of Byzantium during the Year of the Five Emperors, 193 CE. In this turbulent period, the esteemed proconsul of Asia, Asellius Aemilianus, occupied Byzantium in the name of Pescennius Niger, one of the candidates for the emperor's job. Then, Niger made Byzantium his headquarters and refused to surrender to Septimius Severus and go into exile, trusting in the outcome of a military encounter. Byzantium was placed under siege, forcing Niger to abandon the city and retreat to Nicaea. However, Byzantium remained loyal to Niger, and it would take Severus until the end of 195 to finally capture the city.

The second military tombstone, also found within the Theodosius Forum, is the one of an aquilifer of II Adiutrix. An aquilifer was a soldier signifier bearing the eagle standard of a Roman legion. The title is derived from the appearance of the standard, aquila meaning eagle in Latin. The tombstone of this particular standard-bearer states that: "To the [...] spirits of death of Flavius Curillio, helpful and pious standard-bearer to the second legion. He served for 18 years as a soldier and has lived for 40 years. From the same legion the standard-bearer Sanax erected this stele." It stele is even older than the one of the trumpeter as it dates back to the second half of the first century CE. Both tombstones are now in the collections of the Istanbul Archaeological Museum.

Finally, the excavations carried out to dig the foundation trenches of the Faculty of Letters and Sciences of Istanbul University yielded another amazing archaeological discovery: the remains of not one but three basilicas. Unfortunately, their identification has not been possible and thus they are simply called Basilicas "A", "B", and "C". Of the three basilicas, Basilica A has been dated to the reign of Emperor Justinian. This makes it the only basilica of that period whose plan is known: its central space is almost square with two courtyards at the sides. The capitals of the columns separating the basilica's naves resemble those at Hagia Sophia, from the same times. Notably, a large pulpit (ambo) that had been found within Basilica A is the only such piece preserved from the early Byzantine period. Today, to see it, it is necessary to visit the garden of Hagia Sophia.

This text is a fragment of a guidebook to Istanbul: "Byzantine Secrets of Istanbul".