The Lines of Contravallation of Gibraltar (Spanish: Línea de Contravalación de Gibraltar or Línea de Gibraltar), known in English as the "Spanish Lines", were a set of fortifications built by the Spanish across the northern part of the isthmus linking Spain with Gibraltar. They later gave their name to the Spanish town of La Línea de la Concepción. The Lines were constructed after 1730 to establish a defensive barrier across the peninsula, with the aim of preventing any British incursions, and to serve as a base for fresh Spanish attempts to retake Gibraltar. They played an important role in the Great Siege of Gibraltar between 1779 and 1783 when they supported the unsuccessful French and Spanish assault on the British-held fortress.