The imposing stone walls, with added towers for catapults, of a Roman 3rd-century ‘Saxon Shore’ fort. Panoramic views over Breydon Water, into which the fourth wall long since collapsed.
Where the waters of the Yare river and the Waveney unite, in the extreme N.E. of the county, to form the Breydon Broad, there are on the Suffolk shore the splendid remains of a Roman camp, supposed to be the station of Garianonum, and being, with Silchester, Pevensey, and Richborough, the most perfect remains of a Roman work in England. Its ancient name was Cnobersburg, and it is said by Camden to have once contained a Saxon monastery ; but there are no remains of this, nor of the mediaeval castle erected in it in the twelfth century. Ralph, the son of Roger de Burgh, held this castle and the manor by sergeanty, and after him Gilbert de Wiseham had them. At last they were surrendered into the hands of Henry III., who in his twentieth year gave the property to the priory of Bromholm in Norfolk, where it continued till the dissolution of the monasteries. Elizabeth presented it to William Roberts, who sold the place, and it was purchased in late years by Sir J. P. Boileau, Baronet, for the purpose of careful preservation. Grose asserts that the remains of the monastery of Fursans are to be found a short distance N. of the walls.
The ruins consist of the walls, forming the three sides of a rectangular enclosure of nearly 5 acres ; the estuary, whose waters in early ages probably closed the W. front, was sufficient protection on that side, as it is not certain that any wall existed there. The N. and S. wall measure each 107 yards, and that on the E. is 214 yards long, and 9 feet thick, with a height of 14 feet. At each of the corners, and along the E. face, are mural towers, four in all, and one on the N. and S. sides, for flanking purposes. These are built solid, and are 14 feet in diameter; they are disengaged from the wall, but are bonded into it at the top. The one on the N. side has fallen, and is shown to have been built upon oak planking laid on a bed of concrete. A ditch defended the three land sides, the earth of which was made into a mound in the S.W. corner for the Praetorium. Here, perhaps, stood the keep of Ralph de Burgh, whose name the castle bore. Nothing more seems to be known about it. (Castles Of England, Sir James D. Mackenzie, 1896)