Amphipolis in the New Testament
Amphipolis was a Macedonian city, through which Paul and Silas passed, by the Ignatian Way, in journeying from Philippi (33 Roman miles distant) to Thessalonica (Acts 17:1). Their not staying there may have been because there were few, if any, Jews in it: and they hastened on to Thessalonica, "where was a synagogue of Jews," affording the suitable starting point for a Christian church.
It means the city (almost) surrounded by the river Strymon, three miles from its entrance into the sea. An Athenian colony. Its commercial situation, and the neighboring woods of Kerkine, and gold mines of mount Pangtens, gave it importance; also memorable in the Peloponnesian war for the battle fought at it, in which Brasidas and Cleon were killed. The site is now occupied by the village Neokhorio.
International Standard Bible Encyclopedia, which is in the public domain (with minor edits).