Fort Shirley was built by the British from the 1770s onwards to guard Prince Rupert Bay — then one of the most strategically important anchorages in the eastern Caribbean, capable of sheltering an entire fleet. At its peak the complex included barracks, magazines, officers' quarters, a hospital, and gun batteries covering the approaches from sea. The garrison was abandoned in 1854 when the British found the site too unhealthy to maintain, and the jungle claimed most of it within a generation.
The restoration effort that began in the 1980s has uncovered a remarkably complete layout. The powder magazine, the main barracks block, and several of the cannon emplacements have been stabilised and cleared. Walking the site gives a good sense of the original scale — this was a serious military investment, not a small coastal battery. The views from the upper batteries across Prince Rupert Bay are among the best on the island. The fort sits within Cabrits National Park; bring water, as the walk is steep and exposed in places.