The limestone promontory rises 426 metres above the Strait of Gibraltar, its western flank a near-vertical scarp formed during the Jurassic period when tectonic collision pushed sedimentary seabed skyward. Britain claimed the Rock in 1704 under the Treaty of Utrecht, transforming a strategic naval anchorage into Europe's southernmost British Overseas Territory. Today fewer than 34,000 residents occupy the 6.8-square-kilometre peninsula, its economy anchored by financial services, online gaming licenses, and 11 million annual visitors who cross the Spanish border at La Línea. The Upper Rock Nature Reserve protects 40 per cent of Gibraltar's landmass, sheltering Europe's only wild primate population — 230 Barbary macaques descended from North African stock introduced during Moorish occupation. Limestone tunnels excavated by British sappers during the Great Siege of 1779–1783 extend 52 kilometres beneath the summit, sections open for guided tours that reveal gunpowder magazines, water catchments, and siege-era cannon emplacements. St Michael's Cave, a network of cathedral-scale chambers formed by millennia of carbonic acid dissolution, served as Neolithic shelter before conversion to a 600-seat concert hall in 1972. Cross-border excursions from Seville span 210 kilometres through Cádiz and Campo de Gibraltar, requiring passport control at the frontier. Departure coaches typically leave at 08:00, reaching Gibraltar by mid-morning to coordinate with Upper Rock cable-car operations and macaque feeding schedules. The £30 conservation fee, mandatory for all visitors, funds habitat restoration and veterinary care for the macaque troops. Guided itineraries allocate two hours for summit exploration, one hour for Main Street shopping in the duty-free commercial zone, and optional detours to Europa Point, where the lighthouse marks the continent's southernmost tip and views span 23 kilometres to Morocco's Rif Mountains on clear days.