Rayleigh Mount is the surviving earthwork of a Norman castle built shortly after the Conquest by Swein of Essex, one of the most powerful lords in early Norman England. The motte — the mound on which the castle keep originally stood — rises about 15 metres above the surrounding town, and is now maintained as a public open space by the National Trust. The views from the top across the Thames estuary hinterland give a clear sense of why this site was chosen: the ridge commands the surrounding flatlands for miles in every direction.
The castle itself is long gone, but the motte and baileys are clearly legible as earthworks. A small windmill now stands within the grounds (see Rayleigh Windmill). The site is freely accessible during daylight hours. Combined with the Dutch Cottage and the Rayleigh Town Museum at the base of the hill, it makes a complete morning's exploration of the town's historic core.