The 24 acre star shaped Fort Mitchel is one of the largest in the world and it was the cutting edge of military technology when it was completed around 1850. The points of the star shape meant that defenders could arc fire over all parts of the island, making the whole island one effective kill zone. Should anyone get close enough to the Fort, flanking galleries made for ideal sniper positions hovering over enemy troops. And the whole Fort is set down in such a way that it can barely be seen by enemy troops, making it almost impossible to target.
The fort was designed and built by General Vallency, a character of his time who had 4 wives and 14 children.
The work on the Fort began in 1804 when the threat of invasion from Napoleon was very real but it was left incomplete with his defeat at Waterloo. Two earlier forts had been built before hand as the strategic importance of Spike Island was noticed long before Winston Chruchill would call the island 'The sentinel tower of the approaches to Western Europe'.
On its completion the Fort was designed to garrison up to 3000 men, but the famine years drove up the prisoner population and Spike instead had to keep men in rather than keep them out.
The last of the prisoners left in the late 1800's and the Fort was used by both the British and Irish army and Navy over much of the 20th century before becoming a prison again in 1985.
The Fort originally called Fort Westmoreland but it was renamed Fort Mitchel after the Nationalist hero who was a prisoner on Spike in the 1840s.
Today visitors can go through the walls of the fort to the enormous parade ground inside, and many of the buildings and tunnels can be explored as part of you trip to Spike Island.