La Línea de la Concepción is a town in Spain, in the province of Cádiz in Andalucia. It lies on the eastern isthmus of the Bay of Gibraltar, north of the Gibraltar-Spain border, which lies north of the British overseas territory of Gibraltar, with which it has close economic and social links. It is situated on the sandy isthmus which unites the Rock of Gibraltar with the coast in the eastern flank of the Bay of Gibraltar, between Sierra Carbonera and the Rock of Gibraltar.