Originally named Ile a la Raquette (Snowshoe Island), this island located in Halifax harbour was renamed George Island in 1749 after King George II. From the mid-18th century until after World War II, it played a part in the defense of Halifax.
The 1870's brought the latest rifled muzzle-loading (RML) guns, submarine mining headquarters and more. (NOTE: This didn't mean mines to destroy submarines. It meant, explosives placed underwater and triggered remotely to destroy invading ships).
During World War II, the island had anti-aircraft guns.
Update August 6, 2020:
The government has announced that the island will be opened to the public for weekend boat tours. No date for the opening was given. See article attached below from MSN News.
Great thanks to Parks Canada for granting us this quite exclusive opportunity to examine this piece of Canada's history up close!
In it's relatively unmodified state, this is truly something to behold. It's amazing the work that went into these defenses given the technology of the day, and no... no sign of any tunnels leading to the Citadel. ;)