Sardis was once the capital of the powerful Lydian kingdom that dominated much of the Aegean before the Persians arrived. It is also the site of one of the Seven Churches of Revelation (or Apocalypse) mentioned in the New Testament. From 560 BC to 546/7 BC the city was ruled by king Croesus. During his reign, local metallurgists discovered the secret of separating gold from silver, and produced both gold and silver coins of a hitherto unknown purity. This made Sardis rich and Croesus' name became synonymous with wealth itself. For this reason, Sardis is often described as the place where modern currency was invented.