Although small today, Lydford (originally Hlidan) in Devon was in Saxon times an important settlement, one of the four largest towns in the county along with Totnes, Exeter and Barnstable, and was built on a ridge protected on three sides by deep valleys, of the River Lyd and a tributary. The only approach was from the open side, the northeast, which was guarded by a ditch and embankment, still evident today. The defences were further strengthened shortly after the Norman conquest by construction of a small fortification at the west edge of the town, overlooking the river confluence; this had a basic ringwork design, with a few wooden buildings also enclosed by a ditch and embankment, and a fence. The buildings were used primarily for storing grain.
This fort was active for only around a hundred years, and was replaced at the end of the 12th century, by a castle, consisting of a three storey stone tower and an adjacent bailey, protected by another set of ditches and earthworks. The lack of curtain walls or a gatehouse reflects the use of the castle for administration (in particular for taxation of the local tin trade) rather than defence. The castle was owned by the Crown, and was improved in the 1240s, by Richard Earl of Cornwall (son of Edward II), and subsequently had a long history of use, initially as a local government centre, later as a prison; only in the 19th century had the place become ruined, having lost the roof and all the intermediate floors. The remains are now managed by English Heritage, as Lydford Castle and Saxon Town - a lightly visited attraction, close to the much more popular National Trust property at the Lydford Gorge. The stone tower is the centrepiece, but the protected sites also include to the northeastern embankment from the Saxon era, and the site of the earlier Norman ringwork fortification.
Lydford lies just inside the western edge of Dartmoor National Park, one mile from the A386, along a road which continues south, across the River Lyd and alongside the Lydford Gorge. The castle is just west of the local church, St Petrock's, while the embankment from the early Norman fort is a short distance away on the far side. The tower is square in cross-section, with sides 51 feet in length; made of grey granite and looks similar from all angles. The structure is not particularly photogenic, lacking any ornate architectural features, and with only limited interior structures. The rectangular bailey is to the northwest, line by low banks on three sides; beyond, to the north, the land slopes down steeply to the river tributary.
The tower has the appearance of being built on top of a mound, but the banks which surround the base were added as part of the 13th century redesign, covering the lower walls to the height of the first floor, effectively transforming the ground floor into a basement. Entrance is through an arched doorway in the east side, leading to a metal walkway across to the far wall and some spiral steps down to the earthen floor. An original set of stairs within the east wall climbs to a viewing area at second floor level, and another stairway, now inaccessible, once led up further, to the roof. The whole tower is divided by a full height internal wall, and has various windows, fireplaces and garderobes (narrow rooms entirely contained within the external walls). The layout reflects the later use of the castle as a prison; the rooms include prisoner cells, the courtroom, a dining area and several guard chambers. The external walls are about nine feet thick from the base to the first floor, and this section dates from the initial construction in the 12th century; the narrower walls of the two stories above were added as part of the reconfiguration, replacing the existing upper floors.