Area: 6.5 sq km / 2.5 sq ml Language: English Currency: Gibraltar government notes and Pound Sterling Population: 27,776 Literacy rate: Mainly Roman Catholic Physical features: Strategic naval and air base, with NATO underground headquarters and communications centre; colony of Barbary apes; the frontier zone is adjoined by the Spanish port of La Linea Exports: Mainly a trading centre for the import and re - export of goods