mostly mountainous. All other districts have some lowlands. The largest lowland area is located in the south of the province along the lower Côn River. It encompasses much of Quy Nhon, the districts of Tuy Phước, An Nhơn, the western part of Phù Cát, and the eastern part of Tây Sơn. Given its size, and the access to a major port as well as Bình Định's major river, it has long been the place where most of Bình Định's people and economic activities concentrate. It was the site of Vijaya, one of the major city-states of Champa. The majority of Bình Định's population lives in the districts around this plain. Other lowland areas are located in the coastal districts of Hoài Nhơn, Phù Mỹ, Phù Cát, as well as the inland district of Hoài Ân. There are some hills or mountains near the coast in all of the coastal provinces, with the highest peak in Phù Cát at 874m (Ba mountain, núi Bà) and in Phù Mỹ at 602m. Mountains form natural borders to the neighbouring provinces. Cù Mông pass (đèo Cù Mông) is the main border crossing to Phú Yên province. National Route 1 passes through this pass, while there is another road (1D) along the coast. The border to Gia Lai province is the most mountainous, with the only road connection at An Khê pass (đèo An Khê) between the towns of Phú Phong in Tây Sơn district and An Khê in Gia Lai. The border to Quảng Ngãi province is also very mountainous, with the major road and railway passing through Bình Đê Pass (đèo Bình Đê) near Tam Quan. Hydrography Côn River is the largest and most important river in Bình Định. It forms a small delta north of Quy Nhon. Most of it can be used as an inland waterway for transportation. This is probably one of the reasons why a major centre of power of Champa emerged along this river. Other rivers are Lại Giang River at the centre of the lowland areas of Hoài Nhơn and Hoài Ân in northern Bình Định, Mỹ Cát River in central Bình Định, and Hà Thanh River along the valley in Vân Canh district in southern Bình Định. The largest lake is Định Bình Lake, an artificial lake mainly used for irrigation in the highlands of western Bình Định. Also in western Bình Định is Vĩnh Sơn