O'Hara's Battery is in Gibraltar, the British Overseas Territory at the southern end of the Iberian Peninsula.

[3][10][11] O'Hara was replaced as governor later that year by Prince Edward, the Duke of Kent, and future father of Queen Victoria.

[12][13] O'Hara had believed that if he were successful in constructing a watchtower on the highest point of the Rock, the Garrison would be able to observe the enemy at the Spanish port of Cadiz.

The handsome, flamboyant officer who wore the garb of an earlier era has been described as "the most perfect specimen I ever saw of the soldier and courtier of the last age."

[17][18] In 1901, it was replaced by a 9.2 inch Mark X BL gun with a range of 29,000 yards (16 mi), to defend the Strait of Gibraltar.

[22] O'Hara's Battery features a narrow stairway (pictured below) which leads to the door of an underground magazine.

[17] The tunnel (pictured below) between the engine room and the gun not only provides access, but also stores pumps, hoists, and shells.

In May 2012, the Gibraltar Regulatory Authority finalized a contract with United Kingdom-based Arqiva to establish digital broadcasting on the Rock.

The new transmitters will operate from one location on the Upper Rock, replacing two of the existing sites: O'Hara's Battery and Signal Hill.

[18][27] In 2009, visiting servicemen from regiments of the Territorial and Regular Armies spent weeks restoring O'Hara's and Lord Airey's Batteries.