The Normans took over Trani from the Byzantine Empire in the 11th century. From the 11th century until the 13th century, Trani was a rich and very important city. This was especially true when the Holy Roman Emperor Frederick II ruled Trani. Trani was an important port for the Knights Templar during the Crusades. People came from all over Italy to do business there. Many churches, palaces, and castles were built in Trani during this time. Many Jews lived in Trani at this time. There were 200 Jewish families and four big synagogues in the city. Isaiah di Trani, one of the most famous rabbis of the Middle Ages, lived there.