The Greek proper noun Asia (Ἀσία) in the New Testament refers not to the entire continent of Asia but to the Roman province of Asia — located in what is today western Turkey. Its capital was Ephesus. The province was one of the wealthiest and most culturally significant in the Roman Empire.
Asia is central to the New Testament mission. Paul's third missionary journey spent over two years in Ephesus, the capital of Asia, with such effect that "all the Jews and Greeks who lived in the province of Asia heard the word of the Lord" (Acts 19:10). The seven churches addressed in Revelation 1–3 are all in Asia: Ephesus, Smyrna, Pergamum, Thyatira, Sardis, Philadelphia, and Laodicea. This region became the heartland of early Christianity. Paul's letters to the Ephesians and Colossians addressed churches in Asia. The province's centrality in church history reminds us that God often does His most concentrated work in strategic cultural centers.