On this crest (by the present Seraglio Point), commanding the passage to the Euxine, was built, in the seventh century B.C., by colonists from Megara--with whom Dionysius couples the Corinthians--the Acropolis, the sacred city and citadel, and within certain limits the lines of its containing walls may still be traced. The lower city gathered about the slopes outside the Acropolis, and had other walls defining its landward limits. Dionysius, the ancient Byzantine writer, who describes the city before the siege of Severus, 196 A.D., says that this citadel of Byzantium was on the promontory of the Bosporus, above the bay called Keras (the Golden Horn). “At a little distance over the height is the altar of Athena Ecbasia--of the landing--where the colonists fought as for their own land. There is too a temple of Poseidon, an ancient one and hence quite plain, which stands over the sea.... Below the temple of Poseidon, but within the wall, on the level ground are stadia and gymnasia, and courses for the young.”[1] This Acropolis is roughly outlined in Fig. 1, the evidence being the contours of the hill, remains and records of certain walls to be mentioned later, and the boundaries between the first four regions in Constantine’s city as given in the _Notitia_,[2] a description of the city written in the beginning of the fifth century. The Acropolis so defined has a striking resemblance to other Greek hill cities--Tiryns, Mycenae, Acrocorinth, and the Acropolis of Athens. In Fig. 1 the cross shows the site of the present Church of S. Sophia; the arrow shows the Hippodrome, which, still existing, is the great monument of pre-Constantinian times, and forms the key for all study of the subsequent city; O shows the position of the column said to have been erected by Claudius Gothicus about 270 A.D., which stands at the north end of the Acropolis overlooking Seraglio or Demetrius Point. Of the ancient Greek town few positive remains have come down to us, with the exception of the coins. A publication by the Greek Philological Society of Constantinople mentions as among several pre-Constantinian inscriptions a marble slab found in “the tower next to the _Zouk Tsesmé_ gate on the left as one ascends to S. Sophia,” which refers to the stadium erected by Pausanias the General in 477 B.C., “within the walls of Byzantium and below the temple of Poseidon.”[3] The coins also go back to the fifth century B.C. The early ones show a cow standing on a dolphin, with the letters BY. In the third century we have Poseidon seated on a promontory, and later again a dolphin twined round a trident--all the types having evident reference to the sea-washed city. Another relic of ancient Byzantium is still to be seen below the curve of the Hippodrome, where a white marble capital of good Greek Doric work lies neglected on the seaward bank of the new railway.