The 9.2-inch gun of Breakneck Battery

Breakneck Battery, Gibraltar's hidden gun, is a contradiction and a treasure. It was installed on Ministry of Defence property at the Upper Rock Nature Reserve at the turn of the 20th century, where it still sits, pointing towards the Mediterranean. Its purpose was coastal defense and it served as such during both naval and land attacks. Originally, the guns were installed due to the HMS Thunderer's cannon explosion in 1879, which caused a shift in the British military's preferred ordnance system to breech-loading guns.

By the late 20th century, only a few 9.2-inch guns remained across the British Empire. These guns were mounted at strategic locations all over the Empire, and Gibraltar was no different. Outside of Breakneck, O'Hara's, and Lord Airey's batteries remain, all located on Ministry of Defence property. Breakneck Battery is noteworthy as it was refurbished by 10 Signal Regiment in both 2012 and 2016. Despite this, it remains closed to the public as of 2010.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons