This post is all about Camden, not Camden Town in London, but Fort Camden (Camden Fort Meagher) in Crosshaven, County Cork.
Camden is an old fortified fort at the mouth of Cork Harbour, dating back to 1550, when it was known as James’ Battery. In the 18th century it was re-named Fort Camden after the British Earl of Camden, who was Lord Lieutenant of Ireland at the time. You can read the history of Fort Camden, which was re-named Camden Fort Meagher, here.
Most of the fort was built underground, and the Bright Tunnel descents 160 feet underground
There was a magazine underground which stored vast amounts of ammunition and gunpowder, and the granite spiral staircase allowed the soldiers easy access to this magazine in the event of an attack from enemy forces.