The earliest evidence of settlement in the area is a Neolithic site known as 'Ain Ghazal. Its successor was known as "Rabbath Ammon", which was the capital of the Ammonites, then as "Philadelphia", and finally as Amman. It was initially built on seven hills but now spans over 19 hills combining 27 districts, which are administered by the Greater Amman Municipality headed by its mayor Aqel Biltaji. Areas of Amman have either gained their names from the hills (Jabal) or valleys (Wadi) they lie on, such as Jabal Lweibdeh and Wadi Abdoun. East Amman is predominantly filled with historic sites that frequently host cultural activities, while West Amman is more modern and serves as the economic center of the city.