The first vivid appearance of Selymbria in history comes in 410 BCE, when Alcibiades — Athenian general, inveterate schemer, and one of antiquity's most brilliant troublemakers — was operating in the Propontis region. The people of Selymbria refused to open their gates to his army. Rather than force the issue, Alcibiades accepted money from them instead — a pragmatic negotiation that kept the town intact. Some time later, he returned and gained entry through the treachery of townspeople who opened the gates from inside, after which he levied contributions on the inhabitants and installed a garrison. The historian Xenophon also records passing through Selymbria, meeting there with Medosades, the envoy of the Thracian king Seuthes II. The town appears in Demosthenes, too, mentioned as an Athenian ally in 351 BCE. For a place that left little architectural record, it accumulated a remarkable roster of ancient visitors.

Selymbria's most dramatic political moments came during the Byzantine dynastic convulsions of the late fourteenth century. Three rulers used the town as a base at different points, each during periods of contested legitimacy: Andronikos IV Palaiologos held it from 1381 to 1385 after losing the throne of Constantinople; John VII Palaiologos used it from 1385 to 1403 during his own rivalry with his uncle; and Theodore II Palaiologos held it as a despot from 1443 to 1448. The town that refused to admit Alcibiades became, in a later era, a refuge for emperors. The Anastasian Wall — built by Emperor Anastasius I Dicorus to protect Constantinople — ran near Selymbria at its southern end, tethering the town to the larger defensive geography of the Byzantine capital.

Ancient sources preserve a few details about Selymbria that resist easy categorization. Pliny the Elder reported that the town was said to be the birthplace of Prodicus, a disciple of Hippocrates. The poet Polyidos of Selymbria won a dithyramb competition at Athens. Athenaeus, in his gossipy compendium the Deipnosophistae, mentions a Cleisophus of Selymbria who fell in love with a marble statue while visiting Samos — which says nothing about Selymbria itself, but captures something of the eccentric human texture these ancient sources preserve. The city also had its own mint, modest but historically significant enough to be studied by the numismatist Edith Schönert-Geiß. It was also the site of the martyrdom of Saint Agathonicus under the Emperor Maximian, which entered the Christian calendar.

In Christian late antiquity, Selymbria became the seat of a bishop, later elevated to an autocephalous archbishopric. By the time of Emperor Michael VIII Palaiologos, its metropolitan — unnamed in surviving records — was among the prelates who signed the letter to the pope concerning the union of Eastern and Western churches. In 1347, Bishop Methodius of Selymbria was one of the signatories at the Fifth Council of Constantinople, which deposed Patriarch John XIV. The town's religious importance outlasted its political one: Selymbria remains a titular see of the Roman Catholic Church to this day, a diocese without a resident bishop, its name preserved in the administrative memory of a church whose structures outlast the cities that gave them birth.

The modern city of Silivri occupies the same Marmara shoreline as ancient Selymbria, about 65 kilometers west of central Istanbul. The coastline still looks as it would have in antiquity — the blue water stretching south toward the horizon, the European Thracian hills rising behind. Silivri is known today partly for its courthouse and detention facility, where high-profile Turkish legal cases have been tried, and partly for its seafood and its quiet beaches. The Anastasian Wall's remains can still be found in the surrounding landscape. What the ancient city itself looked like is largely lost — the centuries of continuous habitation that preserved its name also erased most of its physical form. Selymbria survives in references, not in stone.