Thyatira
A city located in West Asia Minor approximately 52 miles North East of Smyrna, near the road which was laid from Pergamum to Laodicea. Akhisar in Turkey now holds the position in which it once was. It came under Roman rule in 133 B.C. but was originally established as a Macedonian Colony in the time of Alexander the Great.
It was a great city for trading and was at its "peak" in approximately 100 A.D. Some of the trades they had there were dyeing, clothes making, pottery, and brass working.
In Acts 16:14, Paul comes across a woman named Lydia from Thyatira. She was selling purple cloth. The "purple" was made from madder root.
Jesus calls a woman in their midst "Jezebel". She was teaching them and re-introducing the pagan rituals and practices (such as sexual immorality/adultery) into the church located at Thyatira. Jesus tells the rest of the Christians there who were not misled into her teachings to "hold fast to what you have (referring to their spiritual status)".