Odiham Castle (also known locally as King John's Castle) is a ruined castle situated near Odiham in Hampshire, United Kingdom. It is one of only three fortresses built by King John during his reign. The site was possibly chosen by King John because he had visited the area in 1204 and it lay halfway between Windsor and Winchester. Construction Odiham Castle was built on of land acquired from the local lord, Robert the Parker, by modifying a bend in the River Whitewater. The castle, which took seven years to complete, had a three-storey stone keep, an inner round moat and outer a square moat, as well as two moated baileys. There were also raised banking and palisades. Notably, the stronghold also had a domus regis or king's house. Scrolls held by the Public Record Office indicate that total expenditure between the start of work in 1207 and 1214, when work ceased, amounted to £1,000 (). History In 1215 it was from either Odiham or Windsor that King John rode out to Runnymede, where he met the barons and attached his seal to Magna Carta. A year later Odiham Castle was captured by the French after a two-week siege during the First Barons' War in 1216. The garrison of just 13 surrendered on 9 July 1216. At some point over the next nine years the keep was renovated, possibly to remedy the damage done to it by the French forces. It has been suggested that at the same time the mound on which the keep sat was raised by 5 metres and an inner moat surrounding the keep was added to the defences. However, the inner moat was likely in place prior to the siege. In 1238 Simon de Montfort married King John's daughter Eleanor just two years after she had been granted Odiham by her brother, King Henry III. In the following year a kitchen was added on a bridge over the inner moat and a new hall was added on the outside of the keep. During the same period a second building was constructed over the moat, this time on the south eastern side of the keep, to provide extra living space. In 1263 De Montfort rebelled against Henry and died at the Battle of Evesham in 1265; Eleanor was exiled. Odiham Castle was again retained by the Crown. The castle was also involved in the rebellion led by