During its long history, Amman has been inhabited by several civilizations. The first civilization on record is during the Neolithic period, around 8500 BC, when archaeological discoveries in 'Ain Ghazal, located in eastern Amman, showed evidence of not only a settled life but also the growth of artistic work, which suggests that a well-developed civilization inhabited the city at that time. In the 13th century BC Amman was called Rabbath Ammon or Rabat Amon by the Ammonites. In the Hebrew Bible, it is referred to as Rabbat ʿAmmon (Tiberian Hebrew Rabbaṯ ʿAmmôn). It was later conquered by the Assyrians, followed by the Persians, and then the Greeks. Ptolemy II Philadelphus, the Hellenic ruler of Egypt, renamed it Philadelphia. The city became part of the Nabataean kingdom until 106 AD when Philadelphia came under Roman control and joined the Decapolis. In 326 AD, Christianity became the religion of the empire and Philadelphia became the seat of a bishopric during the beginning of the Byzantine era. One of the churches of this period can be seen on the city's Citadel.Temple of Hercules, Roman Corinthian Columns at Citadel Hill. Philadelphia was renamed Amman during the Ghassanian era, and flourished under the Caliphates (with nearby capital) of the Umayyads (in Damascus) and the Abbasids (in Baghdad). It was then destroyed by several earthquakes and natural disasters and remained a small village and a pile of ruins until the Circassians settlement in 1887. The tide changed when the Ottoman Sultan decided to build the Hejaz railway, linking Damascus and Medina, facilitating both the annual hajj pilgrimage and permanent trade, putting Amman, a major station, back on the commercial map.