into the hillside, to protect the audience from the sun. To the northeast of the theatre was a small odeon. Built at roughly the same time as the theatre, the Odeon had 500 seats and is still in use today for music concerts. Archaeologists speculate that the structure was originally covered with a wooden roof to shield the audience from the weather. The Nymphaeum is situated southwest of the Odeon and served as Philadelphia's chief fountain. The Nymphaeum is believed to have contained a pool which was deep and was continuously refilled with water. During the late Byzantine period in the seventh century, several bishops and churches were based in the city. Islamic Amman (7th–15th centuries) In the 630s, the Rashidun Caliphate conquered the region from the Byzantines, beginning the Islamic era in the Levant. Philadelphia was renamed "Amman" by the Muslims and became part of the district of Jund Dimashq. A large part of the population already spoke Arabic, which facilitated integration into the caliphate, as well as several conversions to Islam. Under the Umayyad caliphs who began their rule in 661 AD, numerous desert castles were established as a means to govern the desert area of modern-day Jordan, several of which are still well-preserved. Amman had already been functioning as an administrative centre. The Umayyads built a large palace on the Amman Citadel hill, known today as the Umayyad Palace. Amman was later destroyed by several earthquakes and natural disasters, including a particularly severe earthquake in 747. The Umayyads were overthrown by the Abbasids three years later. Amman's importance declined by the mid-8th century after damage caused by several earthquakes rendered it uninhabitable. Excavations among the collapsed layer of the Umayyad Palace have revealed remains of kilns from the time of the Abbasids (750–969) and the Fatimids (969–1099). In the late 9th century, Amman was noted as the "capital" of the Balqa by geographer al-Yaqubi. Likewise, in 985, the Jerusalemite historian al-Muqaddasi described Amman as the capital of Balqa, and that it was a town in the desert fringe of Syria surrounded by villages and cornfields and was a regional source of lambs, grain and honey. Furthermore, al-Muqaddasi describes Amman as a "harbor of the desert" where Arab Bedouin would take refuge, and that its citadel, which overlooked the town, contained a small mosque. The occupation of the Citadel Hill by the Crusader Kingdom of Jerusalem is so