The earliest evidence of settlement in Amman comes from a Neolithic site known as 'Ain Ghazal, which reached its height around 7000 BC. During the Iron Age, the city was known as Rabbath Ammon and served as the capital of the Ammonite civilization. In the 3rd century BC, Ptolemy II Philadelphus, Pharoah of Ptolemaic Egypt, rebuilt the city and renamed it "Philadelphia", making it a regional center of Hellenistic culture. Under Roman rule, Philadelphia was one of the ten Greek cities of the Decapolis before being directly ruled as part of Arabia Petraea. The Rashidun Caliphate conquered the city from the Byzantines in the 7th century AD, and gave it its current name of Amman. Throughout most of the Middle Ages, the city alternated between periods of devastation and abandonment and periods of relative prosperity as the center of the Balqa region. Amman was largely abandoned from the 15th century until 1878, when Ottoman authorities began settling Circassian refugees there. 