The castle lies between North Warnborough and the Greywell Tunnel. Parking is possible, and quite close to the canal, but local knowledge or advice is of benefit to assist in finding this spot. 

King John's castle, or Odiham castle as it is sometimes known, was a Norman Royal Palace and strong Castle of note, being built during the period from the end of the 12th century and beginning of the 13th century. It was a much larger complex than that which exists today. 

Some of the stone and flint walls remain, but the only substantial remains of the castle is that of a three storey keep which is of an unusual octagonal design, and was one of only a few such designs in the country. The castle itself was made from up to eight keeps. King John only be remembered for being cruel and for signing of the Magna Carta. 

King John stayed here during the early part of June 1215, resting as he traveled from Winchester to Runnymede, near Windsor, in order to sign the Magna Carta.