Thyatira in Easton's Bible Dictionary

a city of Asia Minor, on the borders of Lydia and Mysia. Its modern name is Ak-hissar, i.e., "white castle." Here was one of the seven churches (Rev. 1:11; 2:18-28). Lydia, the seller of purple, or rather of cloth dyed with this colour, was from this city (Acts 16:14). It was and still is famous for its dyeing. Among the ruins, inscriptions have been found relating to the guild of dyers in that city in ancient times.