Gibraltar-Spain border

The Gibraltar–Spain border is the international boundary between the British Overseas Territory of Gibraltar and the Kingdom of Spain. It is also referred to as "The Fence of Gibraltar" or simply "The Fence".The border runs east-west for a total of 1.2km separating Gibraltar from the neighbouring Spanish municipality of La Línea de la Concepción. Since the United Kingdom is outside the European Union's Schengen Area, Gibraltar is too and therefore, identity checks are required to cross the border.HistoryThe Lines of Contravallation of Gibraltar were built by Spain in 1730 to isolate Gibraltar, the lines were north of the isthmus linking Spain with Gibraltar. The neutral zone between Gibraltar and Spain has since been built on by Spain. These lines were the first form of a border between Gibraltar and Spain.During the Peninsular War in the early 19th century, Spain had initially been allied to France while trying to invade Portugal, but France shortly after turned on its ally, Spain. Forcing the Spanish to ally itself with Great Britain and Portugal against Napoleonic France to regain control of Spain from the French, the Lines of Contravallation of Gibraltar were blown up by the Gibraltar Commanding Royal Engineer Charles Holloway who with permission from Spain began to blast an opening through them on 14 February 1810 to avoid them falling into the hands of the approaching French. Gibraltar, supported by La Linea, became an important base for Spanish fighters against Napoleon's troops. Currently, all that remains of the Lines of Contravallation of Gibraltar are the Ruins of Fort St. Barbara, which is in a recovery phase, while the Fort San Felipe remnants have appeared recently. Fort San Carlos does not seem to have left preserved evidence.