‘This is the first stone of a work which I name the King’s Bastion: may it be as gallantly defended, as I know it will be ably executed’
Major General Robert Boyd, 1773.
When the King’s Bastion was built, it was the most important defensive position of the Rock’s westerly defences. Its shape was based on traditional ideas of bastion fortification: it was a large arrow headed construction which projected from the curtain wall into the sea.
The land in front of the bastion was reclaimed from the sea much later, at the beginning of the 20th Century as part of the works for Gibraltar’s new dockyard, by which time the bastion had changed role. The location of the King’s Bastion is significant because it commanded almost the entirety of Gibraltar’s western sea defences and nearby anchorages. It housed casemates, which were ideal as barrack accommodation, so it became the ideal command post for defending the attacks of the Franco-Spanish floating batteries on 13th September, 1782.
The mid to late 19th Century was a relatively peaceful period in Gibraltar’s history but the King’s Bastion was kept up-to-date, keeping pace with new military technology.
By 1859, twenty five guns were mounted on the bastion. They consisted of seventeen 32 pounders (pdrs), two 10-inch howitzers and six 8-inch smooth bore guns. The most significant alteration was made in 1874 when the embrasures along front faces of the bastion were removed to mount a total of 5 Rifled Muzzle-Loading (RML) guns. By 1878 all five guns were finally in place and remained in commission until 1902. By this time the bastion’s many casemates were no longer used as accommodation, but now housed coal stores and one of Gibraltar’s first electricity generating stations.
The bastion was altered once again in preparation for the 20th Century military conflicts. A number of concrete bunkers were placed on its stone walls and the bastion took on a function as a look-out post but also mounted a 6-pdr 6cwt anti-tank gun. In later times of peace, the bastion took on the duties of saluting battery, using four 25-pdrs for the purpose.
In the 1960s the bastion’s military use came to an end and was once again modified, to house a new, this time civil, power generating station. The station was designed by local architect Natalio Langdon and was opened in October 1961. It closed down during the 1990s and was eventually demolished in 2005. The original bastion façades were then re-exposed.
It opened as a leisure centre in March 2008.
Text taken from the official website, link here where there are some good historic piccies.