The first of these was dug towards the end of the Great Siege of Gibraltar, which lasted from 1779 to 1783.
These strata are the Catalan Bay Shale Formation (youngest), Gibraltar Limestone, Little Bay Shale Formation (oldest), and Dockyard Shale Formation (age unknown). Predominantly of shale, the Catalan Bay Shale Formation also contains thick units composed of either brown calcareous sandstone, soft shaly sandstone interbedded with bluish-black limestone, and interlayered greenish-gray marls and dark gray cherts.Today, the Rock of Gibraltar forms a peninsula jutting out into the Strait of Gibraltar from the southern coast of Spain.The promontory is linked to the continent by means of a sandy tombolo with a maximum elevation of 3 m (9.8 ft).On the suggestion of Sergeant-Major Henry Ince of the Royal Engineers, he had a tunnel bored from a point above Willis's Battery to communicate with the Notch, a natural projection from the North face. There was no intention at first of making embrasures in this tunnel, but an opening was found necessary for ventilation; as soon as it had been made a gun was mounted in it.By the end of the siege, the British had constructed six such embrasures, and mounted four guns.
The Moorish Castle is a relic of Moorish rule over Gibraltar, which lasted for 710 years. The 17th-century Muslim historian Al-Maqqari wrote that upon landing, Tariq burned his ships.