Abdera (Greek: Άβδηρα) is a municipality in the Xanthi regional unit of Thrace, Greece. In classical antiquity, it was a major Greek polis on the Thracian coast. The ancient polis is to be distinguished from the municipality, which was named in its honor. The polis lay 17 km east-northeast of the mouth of the Nestos River, almost directly opposite the island of Thasos. It was a colony placed in previously unsettled Thracian territory, not then a part of Hellas, during the age of Greek colonization. The city that developed from it became of major importance in ancient Greece. After the 4th century AD it declined, contracted to its acropolis, and was abandoned, never to be reoccupied except by archaeologists.