Hurst Castle was originally a low, stone artillery fortress, founded in 1544 by King Henry VIII. Standing on a long shingle spit at the western entrance to the Solent, the central twelve sided tower, is encased by an outer curtain wall flanked by three substantial semicircular bastions and a moat. One of the most advanced Tudor stone artillery forts in the England, it originally had a total of 24 gun ports at ground and moat level. It was occupied by parliamentary forces during the English Civil War and in 1648 King Charles I was held prisoner here. Repairs were made between 1673 and 1675, with alterations being carried out in the 1850s and within the moat is the only surviving caponier, of three built in 1852. In the 1860s, two huge casemated wing batteries of brick and granite, were added to the east and west sides.