Originally a Motte and Bailey structure built in the 12th Century, it's ruins are located in West Grinstead, West Sussex, England. It's name - Knepp, comes from the Old English styling of "Cnaep" - which described the earthen mound upon which it was constructed. Commissioned by King John in 1214, it was originally a two-story Keep. King's Henry III, Edward II and Richard II have all visited or stayed at Knepp Castle during it's lifetime. Most of the actual castle was destroyed by the mid-1720s.
Knepp Castle was surrounded by ditches and mounds (an obvious defensive measure), with ramparts built for additional defense. The moat (which once existed), was supplied by a nearby pond. It was documented that the moat was still somewhat functional as late as the 18th Century.
Today, only a single wall with a reinforced doorway (with a smaller window of sorts above it) - still stands. This may have been part of it's Keep or section.