Berkeley, on many accounts one of the most interesting castles in England, has a very curious shell keep, built round a mound, which thus fills up the lower stage. The wall, the lower part of which is thus a revetment, is strengthened by three half-round mural towers, one of which contains the well, and above it the chapel. This keep is also remarkable for the forebuilding covering its entrance, which contains a tower over the lower or outer gate, at the foot of the staircase. This castle is known to have been built soon after the accession of Henry II., and, though Norman, is, of course, late in the style; Orford and Chilham, Norman keeps of a peculiar character, also have forebuildings. The keep at Pontefract is very peculiar. The castle covers the table-top of an oval knoll, natural, with precipitous sides of rock. At one end, on the edge of the cliff, is placed the mound, now encased partially in masonry. The masonry begins at the foot of the cliff, as a sort of half-round tower, or rather a cluster of roundlets, built as a retaining-wall. Above, the circle of masonry is completed, includes the mound, and forms the shell keep. The base is honeycombed with passages and chambers, cut in the rock, and partly lined with masonry. In its present condition this keep exhibits masonry of both Decorated and Perpendicular date, but its substance, as also some of its adjacent masonry, is evidently late Norman. Restormel is rather a round castle than a shell keep, and more Early English than Norman. On the whole, however, it may be classed with the shells. It occupies a natural knoll, and its ring-wall crests the steep slope; against it are the buildings, and within is an open court. Launceston, also, though Early English, belongs to the shell type. It has a central round tower, and a concentric wall much lower, a sort of _chemise_, the space between the two having been covered in with a flat roof. Possibly Montacute, built by the same lord, may have been after the same pattern; but of Montacute even the ruins have long since perished.