City at the S end of the Bosphorus. The original Greek settlement was located at the elevated E apex of a roughly triangular peninsula bordered on the S by the Propontis (the Sea of Marmara, linking the Bosphorus with the Hellespont or Dardanelles) and on the N by a grand, elongated natural harbor, the Golden Horn (Strab. 7.6.2). The peninsula was in part cut NW-SE by a stream, the Lycus. In late antique times the city expanded W across the hills and valleys of the peninsula, filling it out; the area across the Golden Horn to the N and the nearer European shores of the Bosphorus were built up somewhat, and settlements across the straits in Asia were claimed as suburbs. The commercial significance (shipping, fishing, tolls) of its location and the strategic importance it gained from its superb defensive position (Cass. Dio 75.10; cf. Paus. 4.31.5) explain the considerable role Byzantium played in Classical times and, together with its proximity to the troublesome Danubian and E frontiers, Constantine's decision to devalue Rome's functions and make of Byzantium, henceforth Constantinople, the chief city of the Roman Empire.
There is evidence for prehistoric settlement on the site, but Byzantium proper was founded, sometime in the 7th c. B.C., by Megarians who were probably assisted by groups from other Greek cities. In the late 6th and early 5th c. B.C. it was under Persian control. Subsequently it was usually an Athenian ally, and as such it strenuously resisted Philip II of Macedon in a celebrated siege (340-339 B.C.). During the 2d c. the town sided with Rome in her E wars, and thereafter strategic and economic considerations commended it to Rome's care. In the late 2d c. A.D., however, Byzantium sided with Pescennius Niger, and as a result was besieged by the forces of Septimius Severus for more than two years (Cass. Dio 75.12); after its capitulation Severus all but destroyed it. But it was too important a site to ignore, and soon afterward he began its reconstruction and even enlarged it, and subsequent rulers gave it additional buildings. During the Tetrarchy Byzantium was overshadowed by Nicomedia, but in A.D. 330, after several years of construction on a much enlarged site, it became at Constantine's direction a new and Christian city, for eleven centuries thereafter the seat of the Eastern Roman, Byzantine Empire.
Archaeological information about Greek Byzantium is scarce. Little excavation has been done and little can be, largely because of the superimposition of later structures. The perimeter of the site in Greek times, enclosing the heights upon which the Haghia Sophia and the Ottoman Serai now stand, seems to have been a little less than 2 km in length; the exact line of the walls, with their several gates and 27 towers, cannot now be established (Cass. Dio 75.10.3; cf. Paus. 4.31, and Dion. Byz. 6ff). Almost certainly the Megarian acropolis was within the limits of the Serai. Inside the city walls, chiefly in the N part of the town, there were several temples and sanctuaries, among them those of Zeus, Athena, Poseidon, and Dionysos. Near the center of the W limit of the walls was a square called the Thrakion (Xen. Anab. 7.1.24). Just to the N of this was a strategion. The agora was in the vicinity of Haghia Sophia Square and contained a bronze statue of Helios (Malalas 291ff), also apparently known as the Zeuxippos, a name perpetuated in the area in Byzantine times. Other Greek constructions, such as cisterns, gymnasia, and a stadium are also recorded; there seems also to have been a theater. All these monuments have disappeared, though remains of shrines to Artemis, Aphrodite, and Apollo have been found in excavations between the Haghia Sophia and the Haghia Eirene.
Equally little is known of Roman Byzantium, though it is apparent that practical and political buildings were erected by the Roman government; we hear, for example, of an aqueduct built in the time of Hadrian. The plan of the Roman town cannot be recovered, though some facts about the Severan rebuilding are known; parallels with Severus' enlargement and aggrandizement of Leptis come to mind. At Byzantium he doubled the walled area, moving the land-side N-S wall nearly half a km W of the old Greek line--;its N extremity reached the Golden Horn at a point a little to the E of the present Galata Bridge. It was perhaps then that the agora was given porticos all around, gaining the name of tetrastoon. From it Severus ran a porticoed avenue W to his new wall, presumably to a gate therein. He also began a hippodrome to the SW of the tetrastoon; this, some 450 m long in its final form, was enlarged and finished by Constantine. Severus also built a theater, probably near where the Serai kitchens now stand, and baths, apparently in the style and toward the scale of the imperial baths of the capital; these were placed hard by the NE end of the hippodrome, next to the tetrastoon.
Constantine's estimate of the value and importance of the site after he besieged Licinius there in 324 was even more favorable than that of Severus. He razed the latter's walls, and from about 325 vast resources of men and money were provided to frame and pursue his goal of a new capital, an almost entirely new city five times the area of the Severan town. The new land walls were laid out some 3 km W of the Severan walls, and within this huge enclosure there progressed one of the largest and most important exercises in city-making ever undertaken by Western man, to be continued off and on by Constantine's successors for more than two centuries. In a sense Rome was the model--;there were seven hills, fourteen administrative regions, a comparable building typology and an idealized distribution thereof--;but there were also more specifically Hellenistic and eastern influences at work. Most of this astonishing undertaking has disappeared, but fortunately we have texts that enumerate many buildings and works of art and that describe imperial ceremonies more or less topographically; also, there are precious descriptions by pilgrims and visitors made during and after Byzantine times, and drawings made relatively soon after the Turkish conquest of 1453 which record remains no longer in existence (Richter, Unger, Preger, Ebersolt, Gyllius, Freshfield, etc.).
There were provided a capitolium, a golden milestone, and two senate houses. The tetrastoon became an imperial square, an Augusteon, and Constantine added a large forum of curved plan about 600 m to the W, just beyond the line of the former Severan wall. There a great column of porphyry was erected which carried a statue showing Constantine with the attributes of Apollo; the mutilated shaft still stands (Cemberlitas). The Constantinian city plan cannot be recovered. We know only that the new forum was connected with the Augusteon, probably by a continuation of Severus' avenue, and that to the N and W of the forum arteries fanned out to the Golden Horn and across the widening peninsula to the major gates in the new land walls.
Just N of the Augusteon a large church of basilican plan was begun, the forerunner of the celebrated Haghia Sophia of Justinian's time; Constantine began several other major churches. To the S of the Augusteon, toward the present Mosque of Sultan Ahmed (the Blue Mosque), Constantine built his palace, the Daphne, entered from the Augusteon through a bronze gate (the Chalke) and a guards' quarter. The Daphne was also connected with the hippodrome in that the elevated kathisma or imperial loge there was a part of the palace; in these dispositions (as in others in the new city) one can clearly see the inspiration of Rome, in respect to the physical and symbolic relationships there among the forum, the palace on the Palatine, and the Circus Maximus (with its loges high in the facade of the Domus Augustana above). The sphendone or curved SW end of the Hippodrome, raised on powerful piers and vaults above the ground that falls steeply towards the Marmara, was made into a cistern, as were, then and later, a number of declivities in the city, which were cut to rectangular shape and lined, sometimes vaulted over, in the Roman way.
Everywhere Constantine's people placed works of art and historical monuments brought from other parts of the ancient Graeco-Roman world. At the vast hippodrome one could see, for example, the bronze monument dedicated at Delphi by the victors of Plataiai in 479 B.C.; its spiral stem is still there, standing on the line of the spina of the race course. At the NE end of the hippodrome, near where the fountain of Wilhelm II stands today, the carceres or starting stalls were surmounted by a bronze quadriga, supposedly wrought by Lysippos, whose horses now decorate the facade of San Marco in Venice. Round about, and in the Augusteon, the new forum, and the Baths of Zeuxippos, there were scores of such trophies, giving to the new city the quality of a museum, of being the steward of the past.
After Constantine's death in 337, work on the new city slowed down. Valens (364-78) added an aqueduct, a grand nymphaeum, baths, and apparently a cistern. The aqueduct, along with the Theodosian walls the most visible of the Roman urban constructions, still stands in a section between two of the hills of central Istanbul; this great arcade is almost 1 km long. Theodosius I (379-95) and his family returned to the policies of Constantine. In the 390s a new forum, the Forum Tauri, was built about 700 m W of Constantine's, along the line of the Mese or High Street leading W from the Augusteon (today the Divan Yolu and its extensions). Supported along its S edge by vaulted substructures, the vast Forum Tauri may have been inspired by the Forum of Trajan in Rome; details are lacking. The Forum Tauri contained a huge sculptured column of the Trajanic type of which only bits and precious drawings remain. There was also an elaborate monumental gateway, perhaps in the form of a tetrapylon, of which fragments have been excavated and restored on the Ordu Caddesi in the vicinity of the modern university. Probably the best known of Theodoslus monuments in Constantinople is the obelisk he caused to be placed upon the spina of the hippodrome in the traditional manner. The shaft proper is from Heliopolis in Egypt and dates from the 18th dynasty. It stands on a tall square marble base, the four faces of which are carved in relief. In the bottom zones the circus games are shown, together with a scene of the triumphant raising of the obelisk. Above, at larger scale, the court is shown at the circus. Between are dancers, organ players, and a dense crowd of spectators. This is almost a definitive monument of late antique art, where the qualities of frontality and diagrammatic hierarchy are softened in a style that has not forgotten the humanism and classicism of the Graeco-Roman past.
Arcadius (395-408) added still another forum (in the XII Region, towards the S or Marmara limit of Constantine's land wall). Again the details are unknown, but the mutilated base of Arcadius' column there still exists, together with drawings and comments made by intrepid observers after the Conquest. It was Theodosius II (408-50) who gave Constantinople its most stupendous surviving monument, the great land walls of 413 and 447. They were built ca. 1.5 km W of Constantine's walls and nearly doubled the enclosed area of the city. Subjected to numerous earthquakes, to dilapidation, much repair, and understandable neglect, they still stand, traversing some 7 km from the upper reaches of the Golden Horn to the Marmara shore. In the first campaign the prefect Anthemius built the main wall and its massive towers; in the second the Praetorian Prefect Constantine built the outer, lower walls with their towers, and the ditch or moat. Altogether some 400 towers were constructed (including those of the sea walls). In the late 430s a stout single wall was run around the sea perimeter of the city (lengthy stretches are still visible); these Theodosian fortifications traverse in all almost 20 km.
The main curtain of the great land wall is between 3 and 4 m thick at the base and it rises to an average height of 13 m. Its 96 towers, of varying shapes, are from 16 to 20 m high. To the W of this main construction were the successively lower walls and the moat, the whole system averaging nearly 70 m in width. There were a number of posterns and ten major gates, the most celebrated and elaborate of the latter being the Porta Aurea, quite well preserved today. This, the chief ceremonial entrance to the city, is towards the S extremity of the land walls, about 500 m from the Marmara shore.
The unsculptured column of the emperor Marcian (450-57), standing in the center of old Istanbul, and the lost column of Justinian (527-65) that stood in the Augusteon, continued the imperial traditions. But the many churches, palaces, mosaics, and individual works of art of post-Theodosian date that are still to be seen in Istanbul (or are known through the writers referred to above) lie outside the scope of this article. The Museum of Antiquities, inside the Serai walls, is exceptionally rich in pre-Classical, Greek, and Roman art and finds, not only from Byzantium-Constantinople but from other sites in Turkey as well. In the courts of the Serai there are major architectural elements of the late antique period, and other fragments of the past are scattered around old Istanbul, often lodged in structures of later date. Also, a number of portable works were removed to Venice in the 13th c. (W. L. MACDONALD)
Info: Princeton Encyclopedia
(Princeton Encyclopedia of Classical Sites, from Perseus Project)