Asia Minor, a region that roughly corresponds to modern Turkey, is bordered by the Mediterranean Sea on the west and south, the Black Sea on the north, and the Taurus Mountains on the east. It is a region of rugged mountains and rolling plains. The Romans made Asia Minor a province in their empire. Important cities in the region were Ephesus, Smyrna, Pergamum, Miletus, and Troas. Paul made several excursions into Asia Minor. He preached at Antioch in Pisidia and a number of towns in the eastern part of the province (Acts 13-14) and also founded congregations at various places in Galatia. He spent two years in Ephesus in the western part of Asia Minor (Acts 19). The book of Revelation is a letter that was sent to Christians in seven congregations located in the region (Revelation 1:11).